High availability distributed deduplicated storage system

ABSTRACT

A high availability distributed, deduplicated storage system according to certain embodiments is arranged to include multiple deduplication database media agents. The deduplication database media agents store signatures of data blocks stored in secondary storage. In addition, the deduplication database media agents are configured as failover deduplication database media agents in the event that one of the deduplication database media agents becomes unavailable.

PRIORITY CLAIM

The present application claims priority to U.S. Provisional App. No.61/751,699, filed Jan. 11, 2013, entitled HIGH AVAILABILITY DISTRIBUTEDDEDUPLICATED STORAGE SYSTEM, the entirety of which is incorporatedherein by reference.

BACKGROUND

Businesses worldwide recognize the commercial value of their data andseek reliable, cost-effective ways to protect the information stored ontheir computer networks while minimizing impact on productivity.Protecting information is often part of a routine process that isperformed within an organization.

A company might back up critical computing systems such as databases,file servers, web servers, and so on as part of a daily, weekly, ormonthly maintenance schedule. The company may similarly protectcomputing systems used by each of its employees, such as those used byan accounting department, marketing department, engineering department,and so forth.

Given the rapidly expanding volume of data under management, companiesalso continue to seek innovative techniques for managing data growth, inaddition to protecting data. For instance, companies often implementmigration techniques for moving data to lower cost storage over time anddata reduction techniques for reducing redundant data, pruning lowerpriority data, etc.

Enterprises also increasingly view their stored data as a valuableasset. Along these lines, customers are looking for solutions that notonly protect and manage, but also leverage their data. For instance,solutions providing data analysis capabilities, improved datapresentation and access features, and the like, are in increasingdemand.

In response to these challenges, one technique developed by storagesystem providers is data deduplication. Deduplication typically involveseliminating or reducing the amount of redundant data stored andcommunicated within a storage system, improving storage utilization. Forexample, data can be divided into units of a chosen granularity (e.g.,files or data blocks). As new data enters the system, the data units canbe checked to see if they already exist in the storage system. If thedata unit already exists, instead of storing and/or communicating aduplicate copy, the storage system stores and/or communicates areference to the existing data segment.

SUMMARY

Deduplication can improve storage utilization, system traffic (e.g.,over a networked storage system), or both. Deduplication techniquesdesigned to reduce the demands on storage systems during storageoperations such as backup and/or replication operations can be found inthe following U.S. patent applications, each of which is incorporated byreference in its entirety. One or more embodiments of the presentdisclosure may be used with systems and methods disclosed therein:

-   -   U.S. patent application Ser. No. 12/982,100, entitled “Systems        and Methods for Retaining and Using Block Signatures in Data        Protection Operations,” filed Dec. 30, 2010; and    -   U.S. patent application Ser. No. 12/725,288, entitled        “Extensible Data Deduplication System and Method,” filed Mar.        16, 2010.

As the amount of data increases in systems employing deduplication, theamount of computational and storage overhead involved in managing thededuplication process can become quite significant. For example, as theamount of data increases, there is a corresponding increase in thenumber of deduplication data blocks (or other deduplication data units)to maintain. Moreover, such systems often calculate and store signatures(e.g., hashes of the data blocks) associated with each data block, whichare used to identify and remove redundant data blocks, presentingfurther capacity and maintenance challenges.

In order to address such challenges, a deduplicated storage system isprovided according to certain embodiments that distributes deduplicateddata across multiple, networked media agents. As will be described ingreater detail, the media agents can communicate with one another usinga light-weight, customized communication scheme. Using multiple,distributed media agents for deduplication will generally be referred toas “parallel deduplication” throughout the disclosure.

In some cases, deduplication management information is stored separatelyfrom the deduplicated data, in separate, special purpose networkedstorage nodes, for example. The management information can include,without limitation, data block signatures and associated metadata, andmappings of deduplicated files including pointers to data blocks makingup the respective files and/or data block location information. Themanagement information can also be distributed across multiplemanagement nodes (e.g., deduplication database media agents) in a mannersimilar to the deduplicated data. The distributed nature of thededuplicated data and/or management information enhances scalability,among providing other benefits.

In addition, to increase system availability and reduce the likelihoodthat a backup operation will fail, each of the special purpose networkedstorage nodes can act as a failover for another special purposenetworked storage node. For example, if management information is evenlydistributed across four nodes and one of the nodes becomes unavailable,another one of the four nodes can begin storing the managementinformation that would have been stored in the unavailable node. If thefailover node also becomes unavailable, one (or both) of the remainingtwo nodes can store the management information that would have beenstored in the two unavailable nodes, etc.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating an exemplary informationmanagement system.

FIG. 1B is a detailed view of a primary storage device, a secondarystorage device, and some examples of primary data and secondary copydata.

FIG. 1C is a block diagram of an exemplary information management systemincluding a storage manager, one or more data agents, and one or moremedia agents.

FIG. 1D is a block diagram illustrating a scalable informationmanagement system.

FIG. 1E illustrates certain secondary copy operations according to anexemplary storage policy.

FIGS. 1F-1H are block diagrams illustrating suitable data structuresthat may be employed by the information management system.

FIG. 2A is a block diagram illustrating a scalable informationmanagement system.

FIG. 2B is a logical block diagram illustrative of an embodiment of atechnique for implementing a failover scheme for a group ofdeduplication database media agents

FIG. 3 is a data flow diagram illustrative of the interaction betweenthe various components of the information management system when adeduplication database media agent becomes unavailable, according tocertain embodiments.

FIG. 4 is a flow diagram of a routine implemented by the storage systemfor processing a storage operation and storing data blocks to secondarystorage when a deduplication database media agent is unavailable,according to certain embodiments.

FIG. 5 is a data flow diagram illustrative of the interaction betweenthe various components of the system after an unavailable deduplicationdatabase media agent becomes available, according to certainembodiments.

FIG. 6 is a flow diagram of a routine implemented by the storage systemfor processing a storage operation and storing data blocks to secondarystorage, according to certain embodiments.

FIG. 7 is a block diagram illustrative of an embodiment of multiplededuplication database media agents arranged as logical partitions of aglobal deduplication database, according to certain embodiments.

DETAILED DESCRIPTION

Overview

Generally described, the present disclosure is directed to a system,method, and computer-readable non-transitory storage medium for storingdata to and restoring data from a storage system including adeduplication database. Although various aspects of the disclosure willbe described with regard to examples and embodiments, one skilled in theart will appreciate that the disclosed embodiments and examples shouldnot be construed as limiting.

Each DDB media agent in the system can be assigned its own logicalpartition in a global deduplication database. Furthermore, the systemcan assign the different DDB media agents to store the signatures ofdifferent data blocks. For example, in some embodiments, the system canassign the DDB media agents to store signatures based on a modulooperation performed on the signature of each data block. As an example,and not to be construed as limiting, if there are four DDB media agents(DDB media agent1-DDB media agent4) and modulo 4 is used to assign thesignatures to different DDB media agents, DDB media agent1 can store thesignatures when the modulo operation results in a 0, DDB media agent2can store the signatures that result in a 1, etc.

During a backup, the system determines the signature of each data blockand queries the DDB media agent assigned to store the correspondingsignature based on the modulo operation. If the signature is found, thesystem stores a link to a copy of the data block stored in secondarystorage. If the signature is not found in the assigned DDB media agent,a copy of the data block is stored in secondary storage, and thesignature and a link to the copy of the data block are stored in theassigned DDB media agent.

To increase system availability and reduce the likelihood that a backupoperation will fail, each DDB media agent can act as a failover DDBmedia agent for another DDB media agent. With continued reference to theexample given above, the DDB media agent1 can act as a failover for theDDB media agent4, the DDB media agent2 can act as the failover for theDDB media agent1, the DDB media agent3 for the DDB media agent2, and theDDB media agent4 for the DDB media agent3. Thus, if one of the DDB mediaagents (e.g., DDB media agent1) becomes unavailable (e.g., due to anetwork outage, power outage, hardware/software malfunction, scheduledmaintenance, etc.), the system can use the assigned failover DDB mediaagent (e.g., DDB media agent2) to store signatures that are assigned tobe stored in the unavailable DDB media agent (DDB media agent1) and toverify whether data blocks are already stored in secondary storage.

In addition, if DDB media agent2 becomes unavailable as well, itsassigned failover DDB media agent (e.g., DDB media agent3) can store thesignatures for the two unavailable DDB media agents (DDB media agent1and DDB media agent2) and so on. The system can also use the failoverDDB media agents for database pruning. Accordingly, the system canremain available for backup operations despite the unavailability of oneor more DDB media agents.

Furthermore, once the unavailable DDB media agent becomes available, thesystem can continue to refer to the failover DDB media agent for thesignatures that were stored there while the other DDB media agent wasunavailable. With continued reference to the example given above, thesystem can track the signatures stored in DDB media agent2 as a resultof the unavailability of DDB media agent1. Thus, even when DDB mediaagent1 becomes available, the system can continue to refer to DDB mediaagent2 for the signatures stored thereon while DDB media agent1 wasunavailable. For new signatures and signatures stored on DDB mediaagent1 previously, the system can refer to DDB media agent1.

Information Management System Overview

With the increasing importance of protecting and leveraging data,organizations simply cannot afford to take the risk of losing criticaldata. Moreover, runaway data growth and other modern realities makeprotecting and managing data an increasingly difficult task. There istherefore a need for efficient, powerful, and user-friendly solutionsfor protecting and managing data.

Depending on the size of the organization, there are typically many dataproduction sources which are under the purview of tens, hundreds, oreven thousands of employees or other individuals. In the past,individual employees were sometimes responsible for managing andprotecting their data. A patchwork of hardware and software pointsolutions have been applied in other cases. These solutions were oftenprovided by different vendors and had limited or no interoperability.

Certain embodiments described herein provide systems and methods capableof addressing these and other shortcomings of prior approaches byimplementing unified, organization-wide information management. FIG. 1Ashows one such information management system 100, which generallyincludes combinations of hardware and software configured to protect andmanage data and metadata generated and used by the various computingdevices in the information management system 100.

The organization which employs the information management system 100 maybe a corporation or other business entity, non-profit organization,educational institution, household, governmental agency, or the like.

Generally, the systems and associated components described herein may becompatible with and/or provide some or all of the functionality of thesystems and corresponding components described in one or more of thefollowing U.S. patents and patent application publications assigned toCommVault Systems, Inc., each of which is hereby incorporated in itsentirety by reference herein:

-   -   U.S. Pat. No. 8,285,681, entitled “DATA OBJECT STORE AND SERVER        FOR A CLOUD STORAGE ENVIRONMENT, INCLUDING DATA DEDUPLICATION        AND DATA MANAGEMENT ACROSS MULTIPLE CLOUD STORAGE SITES”;    -   U.S. Pat. No. 8,307,177, entitled “SYSTEMS AND METHODS FOR        MANAGEMENT OF VIRTUALIZATION DATA”;    -   U.S. Pat. No. 7,035,880, entitled “MODULAR BACKUP AND RETRIEVAL        SYSTEM USED IN CONJUNCTION WITH A STORAGE AREA NETWORK”;    -   U.S. Pat. No. 7,343,453, entitled “HIERARCHICAL SYSTEMS AND        METHODS FOR PROVIDING A UNIFIED VIEW OF STORAGE INFORMATION”;    -   U.S. Pat. No. 7,395,282, entitled “HIERARCHICAL BACKUP AND        RETRIEVAL SYSTEM”;    -   U.S. Pat. No. 7,246,207, entitled “SYSTEM AND METHOD FOR        DYNAMICALLY PERFORMING STORAGE OPERATIONS IN A COMPUTER        NETWORK”;    -   U.S. Pat. No. 7,747,579, entitled “METABASE FOR FACILITATING        DATA CLASSIFICATION”;    -   U.S. Pat. No. 8,229,954, entitled “MANAGING COPIES OF DATA”;    -   U.S. Pat. No. 7,617,262, entitled “SYSTEM AND METHODS FOR        MONITORING APPLICATION DATA IN A DATA REPLICATION SYSTEM”;    -   U.S. Pat. No. 7,529,782, entitled “SYSTEM AND METHODS FOR        PERFORMING A SNAPSHOT AND FOR RESTORING DATA”;    -   U.S. Pat. No. 8,230,195, entitled “SYSTEM AND METHOD FOR        PERFORMING AUXILIARY STORAGE OPERATIONS”;    -   U.S. Pat. No. 7,315,923, entitled “SYSTEM AND METHOD FOR        COMBINING DATA STREAMS IN A STORAGE OPERATION”;    -   U.S. Pat. No. 8,364,652, entitled “CONTENT-ALIGNED, BLOCK-BASED        DEDUPLICATION”;    -   U.S. Pat. Pub. No. 2006/0224846, entitled “SYSTEM AND METHOD TO        SUPPORT SINGLE INSTANCE STORAGE OPERATIONS”;    -   U.S. Pat. Pub. No. 2010-0299490, entitled “BLOCK-LEVEL SINGLE        INSTANCING”;    -   U.S. Pat. Pub. No. 2009/0329534, entitled “APPLICATION-AWARE AND        REMOTE SINGLE INSTANCE DATA MANAGEMENT”;    -   U.S. Pat. Pub. No. 2012/0150826, entitled “DISTRIBUTED        DEDUPLICATED STORAGE SYSTEM”;    -   U.S. Pat. Pub. No. 2012/0150818, entitled “CLIENT-SIDE        REPOSITORY IN A NETWORKED DEDUPLICATED STORAGE SYSTEM”;    -   U.S. Pat. No. 8,170,995, entitled “METHOD AND SYSTEM FOR OFFLINE        INDEXING OF CONTENT AND CLASSIFYING STORED DATA”; and    -   U.S. Pat. No. 8,156,086, entitled “SYSTEMS AND METHODS FOR        STORED DATA VERIFICATION”.

The information management system 100 can include a variety of differentcomputing devices. For instance, as will be described in greater detailherein, the information management system 100 can include one or moreclient computing devices 102 and secondary storage computing devices106.

Computing devices can include, without limitation, one or more:workstations, personal computers, desktop computers, or other types ofgenerally fixed computing systems such as mainframe computers andminicomputers.

Other computing devices can include mobile or portable computingdevices, such as one or more laptops, tablet computers, personal dataassistants, mobile phones (such as smartphones), and other mobile orportable computing devices such as embedded computers, set top boxes,vehicle-mounted devices, wearable computers, etc. Computing devices caninclude servers, such as mail servers, file servers, database servers,and web servers.

In some cases, a computing device includes virtualized and/or cloudcomputing resources. For instance, one or more virtual machines may beprovided to the organization by a third-party cloud service vendor. Or,in some embodiments, computing devices can include one or more virtualmachine(s) running on a physical virtual machine host operated by theorganization. As one example, the organization may use one virtualmachine as a database server and another virtual or physical machine asa mail server. A virtual machine manager (VMM) (e.g., a Hypervisor) maymanage the virtual machines, and reside and execute on the virtualmachine host. Examples of techniques for implementing informationmanagement techniques in a cloud computing environment are described inU.S. Pat. No. 8,285,681, which is incorporated by reference herein.Examples of techniques for implementing information managementtechniques in a virtualized computing environment are described in U.S.Pat. No. 8,307,177, also incorporated by reference herein.

The information management system 100 can also include a variety ofstorage devices, including primary storage devices 104 and secondarystorage devices 108, for example. Storage devices can generally be ofany suitable type including, without limitation, disk drives, hard-diskarrays, semiconductor memory (e.g., solid state storage devices),network attached storage (NAS) devices, tape libraries or othermagnetic, non-tape storage devices, optical media storage devices,combinations of the same, and the like. In some embodiments, storagedevices can form part of a distributed file system. In some cases,storage devices are provided in a cloud (e.g., a private cloud or oneoperated by a third-party vendor). A storage device in some casescomprises a disk array or portion thereof.

The illustrated information management system 100 includes one or moreclient computing device 102 having at least one application 110executing thereon, and one or more primary storage devices 104 storingprimary data 112. The client computing device(s) 102 and the primarystorage devices 104 may generally be referred to in some cases as aprimary storage subsystem 117.

Depending on the context, the term “information management system” canrefer to generally all of the illustrated hardware and softwarecomponents. Or, in other instances, the term may refer to only a subsetof the illustrated components.

For instance, in some cases, the information management system 100generally refers to a combination of specialized components used toprotect, move, manage, manipulate, analyze, and/or process data andmetadata generated by the client computing devices 102. However, theinformation management system 100 in some cases does not include theunderlying components that generate and/or store the primary data 112,such as the client computing devices 102 themselves, the applications110 and operating system residing on the client computing devices 102,and the primary storage devices 104. As an example, “informationmanagement system” may sometimes refer to one or more of the followingcomponents and corresponding data structures: storage managers, dataagents, and media agents. These components will be described in furtherdetail below.

Client Computing Devices

There are typically a variety of sources in an organization that producedata to be protected and managed. As just one illustrative example, in acorporate environment such data sources can be employee workstations andcompany servers such as a mail server, a web server, or the like. In theinformation management system 100, the data generation sources includethe one or more client computing devices 102.

The client computing devices 102 may include any of the types ofcomputing devices described above, without limitation, and in some casesthe client computing devices 102 are associated with one or more usersand/or corresponding user accounts, of employees or other individuals.

The information management system 100 generally addresses & handles thedata management and protection needs for the data generated by theclient computing devices 102. However, the use of this term does notimply that the client computing devices 102 cannot be “servers” in otherrespects. For instance, a particular client computing device 102 may actas a server with respect to other devices, such as other clientcomputing devices 102. As just a few examples, the client computingdevices 102 can include mail servers, file servers, database servers,and web servers.

Each client computing device 102 may have one or more applications 110(e.g., software applications) executing thereon which generate andmanipulate the data that is to be protected from loss and managed.

The applications 110 generally facilitate the operations of anorganization (or multiple affiliated organizations), and can include,without limitation, mail server applications (e.g., Microsoft ExchangeServer), file server applications, mail client applications (e.g.,Microsoft Exchange Client), database applications (e.g., SQL, Oracle,SAP, Lotus Notes Database), word processing applications (e.g.,Microsoft Word), spreadsheet applications, financial applications,presentation applications, browser applications, mobile applications,entertainment applications, and so on.

The client computing devices 102 can have at least one operating system(e.g., Microsoft Windows, Mac OS X, iOS, IBM z/OS, Linux, otherUnix-based operating systems, etc.) installed thereon, which may supportor host one or more file systems and other applications 110.

As shown, the client computing devices 102 and other components in theinformation management system 100 can be connected to one another viaone or more communication pathways 114. The communication pathways 114can include one or more networks or other connection types including asany of following, without limitation: the Internet, a wide area network(WAN), a local area network (LAN), a Storage Area Network (SAN), a FibreChannel connection, a Small Computer System Interface (SCSI) connection,a virtual private network (VPN), a token ring or TCP/IP based network,an intranet network, a point-to-point link, a cellular network, awireless data transmission system, a two-way cable system, aninteractive kiosk network, a satellite network, a broadband network, abaseband network, a neural network, other appropriate wired, wireless,or partially wired/wireless computer or telecommunications networks,combinations of the same or the like. The communication pathways 114 insome cases may also include application programming interfaces (APIs)including, e.g., cloud service provider APIs, virtual machine managementAPIs, and hosted service provider APIs.

Primary Data and Exemplary Primary Storage Devices

Primary data 112 according to some embodiments is production data orother “live” data generated by the operating system and otherapplications 110 residing on a client computing device 102. The primarydata 112 is generally stored on the primary storage device(s) 104 and isorganized via a file system supported by the client computing device102. For instance, the client computing device(s) 102 and correspondingapplications 110 may create, access, modify, write, delete, andotherwise use primary data 112. In some cases, some or all of theprimary data 112 can be stored in cloud storage resources.

Primary data 112 is generally in the native format of the sourceapplication 110. According to certain aspects, primary data 112 is aninitial or first (e.g., created before any other copies or before atleast one other copy) stored copy of data generated by the sourceapplication 110. Primary data 112 in some cases is created substantiallydirectly from data generated by the corresponding source applications110.

The primary data 112 may sometimes be referred to as a “primary copy” inthe sense that it is a discrete set of data. However, the use of thisterm does not necessarily imply that the “primary copy” is a copy in thesense that it was copied or otherwise derived from another storedversion.

The primary storage devices 104 storing the primary data 112 may berelatively fast and/or expensive (e.g., a disk drive, a hard-disk array,solid state memory, etc.). In addition, primary data 112 may be intendedfor relatively short term retention (e.g., several hours, days, orweeks).

According to some embodiments, the client computing device 102 canaccess primary data 112 from the primary storage device 104 by makingconventional file system calls via the operating system. Primary data112 representing files may include structured data (e.g., databasefiles), unstructured data (e.g., documents), and/or semi-structureddata. Some specific examples are described below with respect to FIG.1B.

It can be useful in performing certain tasks to organize the primarydata 112 into units of different granularities. In general, primary data112 can include files, directories, file system volumes, data blocks,extents, or any other hierarchies or organizations of data objects. Asused herein, a “data object” can refer to both (1) any file that iscurrently addressable by a file system or that was previouslyaddressable by the file system (e.g., an archive file) and (2) a subsetof such a file (e.g., a data block).

As will be described in further detail, it can also be useful inperforming certain functions of the information management system 100 toaccess and modify metadata within the primary data 112. Metadatagenerally includes information about data objects or characteristicsassociated with the data objects.

Metadata can include, without limitation, one or more of the following:the data owner (e.g., the client or user that generates the data), thelast modified time (e.g., the time of the most recent modification ofthe data object), a data object name (e.g., a file name), a data objectsize (e.g., a number of bytes of data), information about the content(e.g., an indication as to the existence of a particular search term),to/from information for email (e.g., an email sender, recipient, etc.),creation date, file type (e.g., format or application type), lastaccessed time, application type (e.g., type of application thatgenerated the data object), location/network (e.g., a current, past orfuture location of the data object and network pathways to/from the dataobject), frequency of change (e.g., a period in which the data object ismodified), business unit (e.g., a group or department that generates,manages or is otherwise associated with the data object), aginginformation (e.g., a schedule, such as a time period, in which the dataobject is migrated to secondary or long term storage), boot sectors,partition layouts, file location within a file folder directorystructure, user permissions, owners, groups, access control lists[ACLs]), system metadata (e.g., registry information), combinations ofthe same or the other similar information related to the data object.

In addition to metadata generated by or related to file systems andoperating systems, some of the applications 110 and/or other componentsof the information management system 100 maintain indices of metadatafor data objects, e.g., metadata associated with individual emailmessages. Thus, each data object may be associated with correspondingmetadata. The use of metadata to perform classification and otherfunctions is described in greater detail below.

Each of the client computing devices 102 are generally associated withand/or in communication with one or more of the primary storage devices104 storing corresponding primary data 112. A client computing device102 may be considered to be “associated with” or “in communication with”a primary storage device 104 if it is capable of one or more of: routingand/or storing data to the particular primary storage device 104,coordinating the routing and/or storing of data to the particularprimary storage device 104, retrieving data from the particular primarystorage device 104, coordinating the retrieval of data from theparticular primary storage device 104, and modifying and/or deletingdata retrieved from the particular primary storage device 104.

The primary storage devices 104 can include any of the different typesof storage devices described above, or some other kind of suitablestorage device. The primary storage devices 104 may have relatively fastI/O times and/or are relatively expensive in comparison to the secondarystorage devices 108. For example, the information management system 100may generally regularly access data and metadata stored on primarystorage devices 104, whereas data and metadata stored on the secondarystorage devices 108 is accessed relatively less frequently.

In some cases, each primary storage device 104 is dedicated to anassociated client computing device 102. For instance, a primary storagedevice 104 in one embodiment is a local disk drive of a correspondingclient computing device 102. In other cases, one or more primary storagedevices 104 can be shared by multiple client computing devices 102,e.g., via a network such as in a cloud storage implementation. As oneexample, a primary storage device 104 can be a disk array shared by agroup of client computing devices 102, such as one of the followingtypes of disk arrays: EMC Clariion, EMC Symmetrix, EMC Celerra, DellEqualLogic, IBM XIV, NetApp FAS, HP EVA, and HP 3PAR.

The information management system 100 may also include hosted services(not shown), which may be hosted in some cases by an entity other thanthe organization that employs the other components of the informationmanagement system 100. For instance, the hosted services may be providedby various online service providers to the organization. Such serviceproviders can provide services including social networking services,hosted email services, or hosted productivity applications or otherhosted applications).

Hosted services may include software-as-a-service (SaaS),platform-as-a-service (PaaS), application service providers (ASPs),cloud services, or other mechanisms for delivering functionality via anetwork. As it provides services to users, each hosted service maygenerate additional data and metadata under management of theinformation management system 100, e.g., as primary data 112. In somecases, the hosted services may be accessed using one of the applications110. As an example, a hosted mail service may be accessed via browserrunning on a client computing device 102. The hosted services may beimplemented in a variety of computing environments. In some cases, theyare implemented in an environment having a similar arrangement to theinformation management system 100, where various physical and logicalcomponents are distributed over a network.

Secondary Copies and Exemplary Secondary Storage Devices

The primary data 112 stored on the primary storage devices 104 may becompromised in some cases, such as when an employee deliberately oraccidentally deletes or overwrites primary data 112 during their normalcourse of work. Or the primary storage devices 104 can be damaged orotherwise corrupted.

For recovery and/or regulatory compliance purposes, it is thereforeuseful to generate copies of the primary data 112. Accordingly, theinformation management system 100 includes one or more secondary storagecomputing devices 106 and one or more secondary storage devices 108configured to create and store one or more secondary copies 116 of theprimary data 112 and associated metadata. The secondary storagecomputing devices 106 and the secondary storage devices 108 maysometimes be referred to as a secondary storage subsystem 118.

Creation of secondary copies 116 can help in search and analysis effortsand meet other information management goals, such as: restoring dataand/or metadata if an original version (e.g., of primary data 112) islost (e.g., by deletion, corruption, or disaster); allowingpoint-in-time recovery; complying with regulatory data retention andelectronic discovery (e-discovery) requirements; reducing utilizedstorage capacity; facilitating organization and search of data;improving user access to data files across multiple computing devicesand/or hosted services; and implementing data retention policies.

The client computing devices 102 access or receive primary data 112 andcommunicate the data, e.g., over the communication pathways 114, forstorage in the secondary storage device(s) 108.

A secondary copy 116 can comprise a separate stored copy of applicationdata that is derived from one or more earlier created, stored copies(e.g., derived from primary data 112 or another secondary copy 116).Secondary copies 116 can include point-in-time data, and may be intendedfor relatively long-term retention (e.g., weeks, months or years),before some or all of the data is moved to other storage or isdiscarded.

In some cases, a secondary copy 116 is a copy of application datacreated and stored subsequent to at least one other stored instance(e.g., subsequent to corresponding primary data 112 or to anothersecondary copy 116), in a different storage device than at least oneprevious stored copy, and/or remotely from at least one previous storedcopy. In some other cases, secondary copies can be stored in the samestorage device as primary data 112 and/or other previously storedcopies. For example, in one embodiment a disk array capable ofperforming hardware snapshots stores primary data 112 and creates andstores hardware snapshots of the primary data 112 as secondary copies116. Secondary copies 116 may be stored in relatively slow and/or lowcost storage (e.g., magnetic tape). A secondary copy 116 may be storedin a backup or archive format, or in some other format different thanthe native source application format or other primary data format.

In some cases, secondary copies 116 are indexed so users can browse andrestore at another point in time. After creation of a secondary copy 116representative of certain primary data 112, a pointer or other locationindicia (e.g., a stub) may be placed in primary data 112, or beotherwise associated with primary data 112 to indicate the currentlocation on the secondary storage device(s) 108.

Since an instance of a data object or metadata in primary data 112 maychange over time as it is modified by an application 110 (or hostedservice or the operating system), the information management system 100may create and manage multiple secondary copies 116 of a particular dataobject or metadata, each representing the state of the data object inprimary data 112 at a particular point in time. Moreover, since aninstance of a data object in primary data 112 may eventually be deletedfrom the primary storage device 104 and the file system, the informationmanagement system 100 may continue to manage point-in-timerepresentations of that data object, even though the instance in primarydata 112 no longer exists.

For virtualized computing devices the operating system and otherapplications 110 of the client computing device(s) 102 may executewithin or under the management of virtualization software (e.g., a VMM),and the primary storage device(s) 104 may comprise a virtual diskcreated on a physical storage device. The information management system100 may create secondary copies 116 of the files or other data objectsin a virtual disk file and/or secondary copies 116 of the entire virtualdisk file itself (e.g., of an entire .vmdk file).

Secondary copies 116 may be distinguished from corresponding primarydata 112 in a variety of ways, some of which will now be described.First, as discussed, secondary copies 116 can be stored in a differentformat (e.g., backup, archive, or other non-native format) than primarydata 112. For this or other reasons, secondary copies 116 may not bedirectly useable by the applications 110 of the client computing device102, e.g., via standard system calls or otherwise without modification,processing, or other intervention by the information management system100.

Secondary copies 116 are also in some embodiments stored on a secondarystorage device 108 that is inaccessible to the applications 110 runningon the client computing devices 102 (and/or hosted services). Somesecondary copies 116 may be “offline copies,” in that they are notreadily available (e.g. not mounted to tape or disk). Offline copies caninclude copies of data that the information management system 100 canaccess without human intervention (e.g. tapes within an automated tapelibrary, but not yet mounted in a drive), and copies that theinformation management system 100 can access only with at least somehuman intervention (e.g. tapes located at an offsite storage site).

The Use of Intermediate Devices for Creating Secondary Copies

Creating secondary copies can be a challenging task. For instance, therecan be hundreds or thousands of client computing devices 102 continuallygenerating large volumes of primary data 112 to be protected. Also,there can be significant overhead involved in the creation of secondarycopies 116. Moreover, secondary storage devices 108 may be specialpurpose components, and interacting with them can require specializedintelligence.

In some cases, the client computing devices 102 interact directly withthe secondary storage device 108 to create the secondary copies 116.However, in view of the factors described above, this approach cannegatively impact the ability of the client computing devices 102 toserve the applications 110 and produce primary data 112. Further, theclient computing devices 102 may not be optimized for interaction withthe secondary storage devices 108.

Thus, in some embodiments, the information management system 100includes one or more software and/or hardware components which generallyact as intermediaries between the client computing devices 102 and thesecondary storage devices 108. In addition to off-loading certainresponsibilities from the client computing devices 102, theseintermediate components can provide other benefits. For instance, asdiscussed further below with respect to FIG. 1D, distributing some ofthe work involved in creating secondary copies 116 can enhancescalability.

The intermediate components can include one or more secondary storagecomputing devices 106 as shown in FIG. 1A and/or one or more mediaagents, which can be software modules residing on correspondingsecondary storage computing devices 106 (or other appropriate devices).Media agents are discussed below (e.g., with respect to FIGS. 1C-1E).

The secondary storage computing device(s) 106 can comprise any of thecomputing devices described above, without limitation In some cases, thesecondary storage computing device(s) 106 include specialized hardwareand/or software componentry for interacting with the secondary storagedevices 108.

To create a secondary copy 116 involving the copying of data from theprimary storage subsystem 117 to the secondary storage subsystem 118,the client computing device 102 in some embodiments communicates theprimary data 112 to be copied (or a processed version thereof) to thedesignated secondary storage computing device 106, via the communicationpathway 114. The secondary storage computing device 106 in turn conveysthe received data (or a processed version thereof) to the secondarystorage device 108. In some such configurations, the communicationpathway 114 between the client computing device 102 and the secondarystorage computing device 106 comprises a portion of a LAN, WAN or SAN.In other cases, at least some client computing devices 102 communicatedirectly with the secondary storage devices 108 (e.g., via Fibre Channelor SCSI connections). In some other cases, one or more secondary copies116 are created from existing secondary copies, such as in the case ofan auxiliary copy operation, described in greater detail below.

Exemplary Primary Data and an Exemplary Secondary Copy

FIG. 1B is a detailed view showing some specific examples of primarydata stored on the primary storage device(s) 104 and secondary copy datastored on the secondary storage device(s) 108, with other components inthe system removed for the purposes of illustration. Stored on theprimary storage device(s) 104 are primary data objects including wordprocessing documents 119A-B, spreadsheets 120, presentation documents122, video files 124, image files 126, email mailboxes 128 (andcorresponding email messages 129A-C), html/xml or other types of markuplanguage files 130, databases 132 and corresponding tables or other datastructures 133A-133C).

Some or all primary data objects are associated with correspondingmetadata (e.g., “Meta1-11”), which may include file system metadataand/or application specific metadata. Stored on the secondary storagedevice(s) 108 are secondary copy data objects 134A-C which may includecopies of or otherwise represent corresponding primary data objects andmetadata.

As shown, the secondary copy data objects 134A-C can individuallyrepresent more than one primary data object. For example, secondary copydata object 134A represents three separate primary data objects 133C,122 and 129C (represented as 133C′, 122′ and 129C′, respectively).Moreover, as indicated by the prime mark (′), a secondary copy objectmay store a representation of a primary data object or metadatadifferently than the original format, e.g., in a compressed, encrypted,deduplicated, or other modified format.

Exemplary Information Management System Architecture

The information management system 100 can incorporate a variety ofdifferent hardware and software components, which can in turn beorganized with respect to one another in many different configurations,depending on the embodiment. There are critical design choices involvedin specifying the functional responsibilities of the components and therole of each component in the information management system 100. Forinstance, as will be discussed, such design choices can impactperformance as well as the adaptability of the information managementsystem 100 to data growth or other changing circumstances.

FIG. 1C shows an information management system 100 designed according tothese considerations and which includes: a central storage orinformation manager 140 configured to perform certain control functions,one or more data agents 142 executing on the client computing device(s)102 configured to process primary data 112, and one or more media agents144 executing on the one or more secondary storage computing devices 106for performing tasks involving the secondary storage devices 108. Whiledistributing functionality amongst multiple computing devices can havecertain advantages, in other contexts it can be beneficial toconsolidate functionality on the same computing device. As such, invarious other embodiments, one or more of the components shown in FIG.1C as being implemented on separate computing devices are implemented onthe same computing device. In one configuration, a storage manager 140,one or more data agents 142, and one or more media agents 144 are allimplemented on the same computing device. In another embodiment, one ormore data agents 142 and one or more media agents 144 are implemented onthe same computing device, while the storage manager is implemented on aseparate computing device.

Storage Manager

As noted, the number of components in the information management system100 and the amount of data under management can be quite large. Managingthe components and data is therefore a significant task, and a task thatcan grow in an often unpredictable fashion as the quantity of componentsand data scale to meet the needs of the organization.

For these and other reasons, according to certain embodiments,responsibility for controlling the information management system 100, orat least a significant portion of that responsibility, is allocated tothe storage manager 140.

By distributing control functionality in this manner, the storagemanager 140 can be adapted independently according to changingcircumstances. Moreover, a computing device for hosting the storagemanager 140 can be selected to best suit the functions of the storagemanager 140. These and other advantages are described in further detailbelow with respect to FIG. 1D.

The storage manager 140 may be a software module or other application.The storage manager generally initiates, performs, coordinates and/orcontrols storage and other information management operations performedby the information management system 100, e.g., to protect and controlthe primary data 112 and secondary copies 116 of data and metadata.

As shown by the dashed, arrowed lines, the storage manager 140 maycommunicate with and/or control some or all elements of the informationmanagement system 100, such as the data agents 142 and media agents 144.Thus, in certain embodiments, control information originates from thestorage manager 140, whereas payload data and payload metadata isgenerally communicated between the data agents 142 and the media agents144 (or otherwise between the client computing device(s) 102 and thesecondary storage computing device(s) 106), e.g., at the direction ofthe storage manager 140. Control information can generally includeparameters and instructions for carrying out information managementoperations, such as, without limitation, instructions to perform a taskassociated with an operation, timing information specifying when toinitiate a task associated with an operation, data path informationspecifying what components to communicate with or access in carrying outan operation, and the like. Payload data, on the other hand, can includethe actual data involved in the storage operation, such as content datawritten to a secondary storage device 108 in a secondary copy operation.Payload metadata can include any of the types of metadata describedherein, and may be written to a storage device along with the payloadcontent data (e.g., in the form of a header).

In other embodiments, some information management operations arecontrolled by other components in the information management system 100(e.g., the media agent(s) 144 or data agent(s) 142), instead of or incombination with the storage manager 140.

According to certain embodiments, the storage manager provides one ormore of the following functions:

-   -   initiating execution of secondary copy operations;    -   managing secondary storage devices 108 and inventory/capacity of        the same;    -   reporting, searching, and/or classification of data in the        information management system 100;    -   allocating secondary storage devices 108 for secondary storage        operations;    -   monitoring completion of and providing status reporting related        to secondary storage operations;    -   tracking age information relating to secondary copies 116,        secondary storage devices 108, and comparing the age information        against retention guidelines;    -   tracking movement of data within the information management        system 100;    -   tracking logical associations between components in the        information management system 100;    -   protecting metadata associated with the information management        system 100; and    -   implementing operations management functionality.

The storage manager 140 may maintain a database 146 ofmanagement-related data and information management policies 148. Thedatabase 146 may include a management index 150 or other data structurethat stores logical associations between components of the system, userpreferences and/or profiles (e.g., preferences regarding encryption,compression, or deduplication of primary or secondary copy data,preferences regarding the scheduling, type, or other aspects of primaryor secondary copy or other operations, mappings of particularinformation management users or user accounts to certain computingdevices or other components, etc.), management tasks, mediacontainerization, or other useful data. For example, the storage manager140 may use the index 150 to track logical associations between mediaagents 144 and secondary storage devices 108 and/or movement of datafrom primary storage devices 104 to secondary storage devices 108. Forinstance, the storage manager index 150 may store data associating aclient computing device 102 with a particular media agent 144 and/orsecondary storage device 108, as specified in a storage policy.

Administrators and other employees may be able to manually configure andinitiate certain information management operations on an individualbasis. But while this may be acceptable for some recovery operations orother relatively less frequent tasks, it is often not workable forimplementing on-going organization-wide data protection and management.

Thus, the information management system 100 may utilize informationmanagement policies 148 for specifying and executing informationmanagement operations (e.g., on an automated basis). Generally, aninformation management policy 148 can include a data structure or otherinformation source that specifies a set of parameters (e.g., criteriaand rules) associated with storage or other information managementoperations.

The storage manager database 146 may maintain the information managementpolicies 148 and associated data, although the information managementpolicies 148 can be stored in any appropriate location. For instance, astorage policy may be stored as metadata in a media agent database 152or in a secondary storage device 108 (e.g., as an archive copy) for usein restore operations or other information management operations,depending on the embodiment. Information management policies 148 aredescribed further below.

According to certain embodiments, the storage manager database 146comprises a relational database (e.g., an SQL database) for trackingmetadata, such as metadata associated with secondary copy operations(e.g., what client computing devices 102 and corresponding data wereprotected). This and other metadata may additionally be stored in otherlocations, such as at the secondary storage computing devices 106 or onthe secondary storage devices 108, allowing data recovery without theuse of the storage manager 140.

As shown, the storage manager 140 may include a jobs agent 156, a userinterface 158, and a management agent 154, all of which may beimplemented as interconnected software modules or application programs.

The jobs agent 156 in some embodiments initiates, controls, and/ormonitors the status of some or all storage or other informationmanagement operations previously performed, currently being performed,or scheduled to be performed by the information management system 100.For instance, the jobs agent 156 may access information managementpolicies 148 to determine when and how to initiate and control secondarycopy and other information management operations, as will be discussedfurther.

The user interface 158 may include information processing and displaysoftware, such as a graphical user interface (“GUI”), an applicationprogram interface (“API”), or other interactive interface through whichusers and system processes can retrieve information about the status ofinformation management operations (e.g., storage operations) or issueinstructions to the information management system 100 and itsconstituent components.

Via the user interface 158, users may optionally issue instructions tothe components in the information management system 100 regardingperformance of storage and recovery operations. For example, a user maymodify a schedule concerning the number of pending secondary copyoperations. As another example, a user may employ the GUI to view thestatus of pending storage operations or to monitor the status of certaincomponents in the information management system 100 (e.g., the amount ofcapacity left in a storage device).

The storage manager 140 may also track information that permits it toselect, designate, or otherwise identify content indices, deduplicationdatabases, or similar databases or resources or data sets within itsinformation management “cell” (or another cell) to be searched inresponse to certain queries. Such queries may be entered by the user viainteraction with the user interface 158. An information management cellmay generally include a logical and/or physical grouping of acombination of hardware and software components associated withperforming information management operations on electronic data. Forinstance, the components shown in FIG. 1C may together form aninformation management cell. Multiple cells may be organizedhierarchically. With this configuration, cells may inherit propertiesfrom hierarchically superior cells or be controlled by other cells inthe hierarchy (automatically or otherwise). Alternatively, in someembodiments, cells may inherit or otherwise be associated withinformation management policies, preferences, information managementmetrics, or other properties or characteristics according to theirrelative position in a hierarchy of storage operation cells. Cells mayalso be delineated and/or organized hierarchically according tofunction, geography, architectural considerations, or other factorsuseful or desirable in performing information management operations. Afirst cell may represent a geographic segment of an enterprise, such asa Chicago office, and a second storage operation cell may represent adifferent geographic segment, such as a New York office. Other cells mayrepresent departments within a particular office. Where delineated byfunction, a first cell may perform one or more first types ofinformation management operations (e.g., one or more first types ofsecondary or other copies), and a second cell may perform one or moresecond types of information management operations (e.g., one or moresecond types of secondary or other copies).

In general, the management agent 154 allows multiple informationmanagement cells 100 to communicate with one another. For example, theinformation management system 100 in some cases may be one informationmanagement cell of a network of multiple cells adjacent to one anotheror otherwise logically related in a WAN or LAN. With this arrangement,the cells may be connected to one another through respective managementagents 154.

For instance, the management agent 154 can provide the storage manager140 with the ability to communicate with other components within theinformation management system 100 (and/or other cells within a largerinformation management system) via network protocols and applicationprogramming interfaces (“APIs”) including, e.g., HTTP, HTTPS, FTP, REST,virtualization software APIs, cloud service provider APIs, and hostedservice provider APIs. Inter-cell communication and hierarchy isdescribed in greater detail in U.S. Pat. No. 7,035,880, which isincorporated by reference herein.

Data Agents

As discussed, a variety of different types of applications 110 canreside on a given client computing device 102, including operatingsystems, database applications, e-mail applications, and virtualmachines, just to name a few. And, as part of the process of creatingand restoring secondary copies 116, the client computing devices 102 maybe tasked with processing and preparing the primary data 112 from thesevarious different applications 110. Moreover, the nature of theprocessing/preparation can differ across clients and application types,e.g., due to inherent structural and formatting differences betweenapplications 110.

The one or more data agent(s) 142 are therefore advantageouslyconfigured in some embodiments to assist in the performance ofinformation management operations based on the type of data that isbeing protected, at a client-specific and/or application-specific level.

The data agent 142 may be a software module or component that isgenerally responsible for managing, initiating, or otherwise assistingin the performance of information management operations. For instance,the data agent 142 may take part in performing data storage operationssuch as the copying, archiving, migrating, replicating of primary data112 stored in the primary storage device(s) 104. The data agent 142 mayreceive control information from the storage manager 140, such ascommands to transfer copies of data objects, metadata, and other payloaddata to the media agents 144.

In some embodiments, a data agent 142 may be distributed between theclient computing device 102 and storage manager 140 (and any otherintermediate components) or may be deployed from a remote location orits functions approximated by a remote process that performs some or allof the functions of data agent 142. In addition, a data agent 142 mayperform some functions provided by a media agent 144, or may performother functions such as encryption and deduplication.

As indicated, each data agent 142 may be specialized for a particularapplication 110, and the system can employ multiple application-specificdata agents 142, each of which may perform information managementoperations (e.g., perform backup, migration, and data recovery)associated with a different application 110. For instance, differentindividual data agents 142 may be designed to handle Microsoft Exchangedata, Lotus Notes data, Microsoft Windows file system data, MicrosoftActive Directory Objects data, SQL Server data, SharePoint data, Oracledatabase data, SAP database data, virtual machines and/or associateddata, and other types of data.

A file system data agent, for example, may handle data files and/orother file system information. If a client computing device 102 has twoor more types of data, one data agent 142 may be used for each data typeto copy, archive, migrate, and restore the client computing device 102data. For example, to backup, migrate, and restore all of the data on aMicrosoft Exchange server, the client computing device 102 may use oneMicrosoft Exchange Mailbox data agent 142 to backup the Exchangemailboxes, one Microsoft Exchange Database data agent 142 to backup theExchange databases, one Microsoft Exchange Public Folder data agent 142to backup the Exchange Public Folders, and one Microsoft Windows FileSystem data agent 142 to backup the file system of the client computingdevice 102. In such embodiments, these data agents 142 may be treated asfour separate data agents 142 even though they reside on the same clientcomputing device 102.

Other embodiments may employ one or more generic data agents 142 thatcan handle and process data from two or more different applications 110,or that can handle and process multiple data types, instead of or inaddition to using specialized data agents 142. For example, one genericdata agent 142 may be used to back up, migrate and restore MicrosoftExchange Mailbox data and Microsoft Exchange Database data while anothergeneric data agent may handle Microsoft Exchange Public Folder data andMicrosoft Windows File System data.

Each data agent 142 may be configured to access data and/or metadatastored in the primary storage device(s) 104 associated with the dataagent 142 and process the data as appropriate. For example, during asecondary copy operation, the data agent 142 may arrange or assemble thedata and metadata into one or more files having a certain format (e.g.,a particular backup or archive format) before transferring the file(s)to a media agent 144 or other component. The file(s) may include a listof files or other metadata. Each data agent 142 can also assist inrestoring data or metadata to primary storage devices 104 from asecondary copy 116. For instance, the data agent 142 may operate inconjunction with the storage manager 140 and one or more of the mediaagents 144 to restore data from secondary storage device(s) 108.

Media Agents

As indicated above with respect to FIG. 1A, off-loading certainresponsibilities from the client computing devices 102 to intermediatecomponents such as the media agent(s) 144 can provide a number ofbenefits including improved client computing device 102 operation,faster secondary copy operation performance, and enhanced scalability.As one specific example which will be discussed below in further detail,the media agent 144 can act as a local cache of copied data and/ormetadata that it has stored to the secondary storage device(s) 108,providing improved restore capabilities.

Generally speaking, a media agent 144 may be implemented as a softwaremodule that manages, coordinates, and facilitates the transmission ofdata, as directed by the storage manager 140, between a client computingdevice 102 and one or more secondary storage devices 108. Whereas thestorage manager 140 controls the operation of the information managementsystem 100, the media agent 144 generally provides a portal to secondarystorage devices 108. For instance, other components in the systeminteract with the media agents 144 to gain access data stored on thesecondary storage devices 108, whether it be for the purposes ofreading, writing, modifying, or deleting data. Moreover, as will bedescribed further, media agents 144 can generate and store data andmetadata data that generally provides insight into the data stored onassociated secondary storage devices 108.

Media agents 144 can comprise separate nodes in the informationmanagement system 100 (e.g., nodes that are separate from the clientcomputing devices 102, storage manager 140, and/or secondary storagedevices 108). In general, a node within the information managementsystem 100 can be a logically and/or physically separate component, andin some cases is a component that is individually addressable orotherwise identifiable. In addition, each media agent 144 may reside ona dedicated secondary storage computing device 106 in some cases, whilein other embodiments a plurality of media agents 144 reside on the samesecondary storage computing device 106.

A media agent 144 (and corresponding media agent database 152) may beconsidered to be “associated with” a particular secondary storage device108 if that media agent 144 is capable of one or more of: routing and/orstoring data to the particular secondary storage device 108,coordinating the routing and/or storing of data to the particularsecondary storage device 108, retrieving data from the particularsecondary storage device 108, coordinating the retrieval of data from aparticular secondary storage device 108, and modifying and/or deletingdata retrieved from the particular secondary storage device 104.

While media agent(s) 144 are generally associated with one or moresecondary storage devices 108, one or more media agents 144 in certainembodiments are physically separate from the secondary storage devices108. For instance, the media agents 144 may reside on secondary storagecomputing devices 106 having different housings or packages than thesecondary storage devices 108. In one example, a media agent 144 resideson a first server computer and is in communication with a secondarystorage device(s) 108 residing in a separate, rack-mounted RAID-basedsystem.

Where the information management system 100 includes multiple mediaagents 144 (FIG. 1D), a first media agent 144 may provide failoverfunctionality for a second, failed media agent 144. In addition, mediaagents 144 can be dynamically selected for storage operations to provideload balancing. Failover and load balancing are described in greaterdetail below.

In operation, a media agent 144 associated with a particular secondarystorage device 108 may instruct the secondary storage device 108 toperform an information management operation. For instance, a media agent144 may instruct a tape library to use a robotic arm or other retrievalmeans to load or eject a certain storage media, and to subsequentlyarchive, migrate, or retrieve data to or from that media, e.g., for thepurpose of restoring the data to a client computing device 102. Asanother example, a secondary storage device 108 may include an array ofhard disk drives or solid state drives organized in a RAIDconfiguration, and the media agent 144 may forward a logical unit number(LUN) and other appropriate information to the array, which uses thereceived information to execute the desired storage operation. The mediaagent 144 may communicate with a secondary storage device 108 via asuitable communications link, such as a SCSI or Fiber Channel link.

As shown, each media agent 144 may maintain an associated media agentdatabase 152. The media agent database 152 may be stored in a disk orother storage device (not shown) that is local to the secondary storagecomputing device 106 on which the media agent 144 resides. In othercases, the media agent database 152 is stored remotely from thesecondary storage computing device 106.

The media agent database 152 can include, among other things, an index153 including data generated during secondary copy operations and otherstorage or information management operations. The index 153 provides amedia agent 144 or other component with a fast and efficient mechanismfor locating secondary copies 116 or other data stored in the secondarystorage devices 108. In some cases, the index 153 does not form a partof and is instead separate from the media agent database 152.

A media agent index 153 or other data structure associated with theparticular media agent 144 may include information about the storeddata. For instance, for each secondary copy 116, the index 153 mayinclude metadata such as a list of the data objects (e.g.,files/subdirectories, database objects, mailbox objects, etc.), a pathto the secondary copy 116 on the corresponding secondary storage device108, location information indicating where the data objects are storedin the secondary storage device 108, when the data objects were createdor modified, etc. Thus, the index 153 includes metadata associated withthe secondary copies 116 that is readily available for use in storageoperations and other activities without having to be first retrievedfrom the secondary storage device 108. In yet further embodiments, someor all of the data in the index 153 may instead or additionally bestored along with the data in a secondary storage device 108, e.g., witha copy of the index 153. In some embodiments, the secondary storagedevices 108 can include sufficient information to perform a “bare metalrestore”, where the operating system of a failed client computing device102 or other restore target is automatically rebuilt as part of arestore operation.

Because the index 153 maintained in the database 152 may operate as acache, it can also be referred to as an index cache. In such cases,information stored in the index cache 153 typically comprises data thatreflects certain particulars about storage operations that have occurredrelatively recently. After some triggering event, such as after acertain period of time elapses, or the index cache 153 reaches aparticular size, the index cache 153 may be copied or migrated to asecondary storage device(s) 108. This information may need to beretrieved and uploaded back into the index cache 153 or otherwiserestored to a media agent 144 to facilitate retrieval of data from thesecondary storage device(s) 108. In some embodiments, the cachedinformation may include format or containerization information relatedto archives or other files stored on the storage device(s) 108. In thismanner, the index cache 153 allows for accelerated restores.

In some alternative embodiments the media agent 144 generally acts as acoordinator or facilitator of storage operations between clientcomputing devices 102 and corresponding secondary storage devices 108,but does not actually write the data to the secondary storage device108. For instance, the storage manager 140 (or the media agent 144) mayinstruct a client computing device 102 and secondary storage device 108to communicate with one another directly. In such a case the clientcomputing device 102 transmits the data directly or via one or moreintermediary components to the secondary storage device 108 according tothe received instructions, and vice versa. In some such cases, the mediaagent 144 may still receive, process, and/or maintain metadata relatedto the storage operations. Moreover, in these embodiments, the payloaddata can flow through the media agent 144 for the purposes of populatingthe index cache 153 maintained in the media agent database 152, but notfor writing to the secondary storage device 108.

The media agent 144 and/or other components such as the storage manager140 may in some cases incorporate additional functionality, such as dataclassification, content indexing, deduplication, encryption,compression, and the like. Further details regarding these and otherfunctions are described below.

Distributed, Scalable Architecture

As described, certain functions of the information management system 100can be distributed amongst various physical and/or logical components inthe system. For instance, one or more of the storage manager 140, dataagents 142, and media agents 144 may reside on computing devices thatare physically separate from one another. This architecture can providea number of benefits.

For instance, hardware and software design choices for each distributedcomponent can be targeted to suit its particular function. The secondarycomputing devices 106 on which the media agents 144 reside can betailored for interaction with associated secondary storage devices 108and provide fast index cache operation, among other specific tasks.Similarly, the client computing device(s) 102 can be selected toeffectively service the applications 110 residing thereon, in order toefficiently produce and store primary data 112.

Moreover, in some cases, one or more of the individual components in theinformation management system 100 can be distributed to multiple,separate computing devices. As one example, for large file systems wherethe amount of data stored in the storage management database 146 isrelatively large, the management database 146 may be migrated to orotherwise reside on a specialized database server (e.g., an SQL server)separate from a server that implements the other functions of thestorage manager 140. This configuration can provide added protectionbecause the database 146 can be protected with standard databaseutilities (e.g., SQL log shipping or database replication) independentfrom other functions of the storage manager 140. The database 146 can beefficiently replicated to a remote site for use in the event of adisaster or other data loss incident at the primary site. Or thedatabase 146 can be replicated to another computing device within thesame site, such as to a higher performance machine in the event that astorage manager host device can no longer service the needs of a growinginformation management system 100.

The distributed architecture also provides both scalability andefficient component utilization. FIG. 1D shows an embodiment of theinformation management system 100 including a plurality of clientcomputing devices 102 and associated data agents 142 as well as aplurality of secondary storage computing devices 106 and associatedmedia agents 144.

Additional components can be added or subtracted based on the evolvingneeds of the information management system 100. For instance, dependingon where bottlenecks are identified, administrators can add additionalclient computing devices 102, secondary storage devices 106 (andcorresponding media agents 144), and/or secondary storage devices 108.Moreover, where multiple fungible components are available, loadbalancing can be implemented to dynamically address identifiedbottlenecks. As an example, the storage manager 140 may dynamicallyselect which media agents 144 and/or secondary storage devices 108 touse for storage operations based on a processing load analysis of themedia agents 144 and/or secondary storage devices 108, respectively.

Moreover, each client computing device 102 in some embodiments cancommunicate with, among other components, any of the media agents 144,e.g., as directed by the storage manager 140. And each media agent 144may be able to communicate with, among other components, any of thesecondary storage devices 108, e.g., as directed by the storage manager140. Thus, operations can be routed to the secondary storage devices 108in a dynamic and highly flexible manner, to provide load balancing,failover, and the like. Further examples of scalable systems capable ofdynamic storage operations, and of systems capable of performing loadbalancing and fail over are provided in U.S. Pat. No. 7,246,207, whichis incorporated by reference herein.

In alternative configurations, certain components are not distributedand may instead reside and execute on the same computing device. Forexample, in some embodiments one or more data agents 142 and the storagemanager 140 reside on the same client computing device 102. In anotherembodiment, one or more data agents 142 and one or more media agents 144reside on a single computing device.

Exemplary Types of Information Management Operations

In order to protect and leverage stored data, the information managementsystem 100 can be configured to perform a variety of informationmanagement operations. As will be described, these operations cangenerally include secondary copy and other data movement operations,processing and data manipulation operations, analysis, reporting, andmanagement operations.

Data Movement Operations

Data movement operations according to certain embodiments are generallyoperations that involve the copying or migration of data (e.g., payloaddata) between different locations in the information management system100 in an original/native and/or one or more different formats. Forexample, data movement operations can include operations in which storeddata is copied, migrated, or otherwise transferred from one or morefirst storage devices to one or more second storage devices, such asfrom primary storage device(s) 104 to secondary storage device(s) 108,from secondary storage device(s) 108 to different secondary storagedevice(s) 108, from secondary storage devices 108 to primary storagedevices 104, or from primary storage device(s) 104 to different primarystorage device(s) 104.

Data movement operations can include by way of example, backupoperations, archive operations, information lifecycle managementoperations such as hierarchical storage management operations,replication operations (e.g., continuous data replication operations),snapshot operations, deduplication or single-instancing operations,auxiliary copy operations, and the like. As will be discussed, some ofthese operations involve the copying, migration or other movement ofdata, without actually creating multiple, distinct copies. Nonetheless,some or all of these operations are referred to as “copy” operations forsimplicity.

Backup Operations

A backup operation creates a copy of a version of data (e.g., one ormore files or other data units) in primary data 112 at a particularpoint in time. Each subsequent backup copy may be maintainedindependently of the first. Further, a backup copy in some embodimentsis generally stored in a form that is different than the native format,e.g., a backup format. This can be in contrast to the version in primarydata 112 from which the backup copy is derived, and which may instead bestored in a native format of the source application(s) 110. In variouscases, backup copies can be stored in a format in which the data iscompressed, encrypted, deduplicated, and/or otherwise modified from theoriginal application format. For example, a backup copy may be stored ina backup format that facilitates compression and/or efficient long-termstorage.

Backup copies can have relatively long retention periods as compared toprimary data 112, and may be stored on media with slower retrieval timesthan primary data 112 and certain other types of secondary copies 116.On the other hand, backups may have relatively shorter retention periodsthan some other types of secondary copies 116, such as archive copies(described below). Backups may sometimes be stored at on offsitelocation.

Backup operations can include full, synthetic or incremental backups. Afull backup in some embodiments is generally a complete image of thedata to be protected. However, because full backup copies can consume arelatively large amount of storage, it can be useful to use a fullbackup copy as a baseline and only store changes relative to the fullbackup copy for subsequent backup copies.

For instance, a differential backup operation (or cumulative incrementalbackup operation) tracks and stores changes that have occurred since thelast full backup. Differential backups can grow quickly in size, but canprovide relatively efficient restore times because a restore can becompleted in some cases using only the full backup copy and the latestdifferential copy.

An incremental backup operation generally tracks and stores changessince the most recent backup copy of any type, which can greatly reducestorage utilization. In some cases, however, restore times can berelatively long in comparison to full or differential backups becausecompleting a restore operation may involve accessing a full backup inaddition to multiple incremental backups.

Any of the above types of backup operations can be at the volume-level,file-level, or block-level. Volume level backup operations generallyinvolve the copying of a data volume (e.g., a logical disk or partition)as a whole. In a file-level backup, the information management system100 may generally track changes to individual files at the file-level,and includes copies of files in the backup copy. In the case of ablock-level backup, files are broken into constituent blocks, andchanges are tracked at the block-level. Upon restore, the informationmanagement system 100 reassembles the blocks into files in a transparentfashion.

Far less data may actually be transferred and copied to the secondarystorage devices 108 during a file-level copy than a volume-level copy.Likewise, a block-level copy may involve the transfer of less data thana file-level copy, resulting in faster execution times. However,restoring a relatively higher-granularity copy can result in longerrestore times. For instance, when restoring a block-level copy, theprocess of locating constituent blocks can sometimes result in longerrestore times as compared to file-level backups. Similar to backupoperations, the other types of secondary copy operations describedherein can also be implemented at either the volume-level, file-level,or block-level.

Archive Operations

Because backup operations generally involve maintaining a version of thecopied data in primary data 112 and also maintaining backup copies insecondary storage device(s) 108, they can consume significant storagecapacity. To help reduce storage consumption, an archive operationaccording to certain embodiments creates a secondary copy 116 by bothcopying and removing source data. Or, seen another way, archiveoperations can involve moving some or all of the source data to thearchive destination. Thus, data satisfying criteria for removal (e.g.,data of a threshold age or size) from the source copy may be removedfrom source storage. Archive copies are sometimes stored in an archiveformat or other non-native application format. The source data may beprimary data 112 or a secondary copy 116, depending on the situation. Aswith backup copies, archive copies can be stored in a format in whichthe data is compressed, encrypted, deduplicated, and/or otherwisemodified from the original application format.

In addition, archive copies may be retained for relatively long periodsof time (e.g., years) and, in some cases, are never deleted. Archivecopies are generally retained for longer periods of time than backupcopies, for example. In certain embodiments, archive copies may be madeand kept for extended periods in order to meet compliance regulations.

Moreover, when primary data 112 is archived, in some cases the archivedprimary data 112 or a portion thereof is deleted when creating thearchive copy. Thus, archiving can serve the purpose of freeing up spacein the primary storage device(s) 104. Similarly, when a secondary copy116 is archived, the secondary copy 116 may be deleted, and an archivecopy can therefore serve the purpose of freeing up space in secondarystorage device(s) 108. In contrast, source copies often remain intactwhen creating backup copies. Examples of compatible data archivingoperations are provided in U.S. Pat. No. 7,107,298, entitled “SYSTEM ANDMETHOD FOR ARCHIVING OBJECTS IN AN INFORMATION STORE”, which isincorporated by reference herein.

Snapshot Operations

Snapshot operations can provide a relatively lightweight, efficientmechanism for protecting data. From an end-user viewpoint, a snapshotmay be thought of as an “instant” image of the primary data 112 at agiven point in time. In one embodiment, a snapshot may generally capturethe directory structure of an object in primary data 112 such as a fileor volume or other data set at a particular moment in time and may alsopreserve file attributes and contents. A snapshot in some cases iscreated relatively quickly, e.g., substantially instantly, using aminimum amount of file space, but may still function as a conventionalfile system backup.

A “hardware” snapshot operation can be a snapshot operation where atarget storage device (e.g., a primary storage device 104 or a secondarystorage device 108) performs the snapshot operation in a self-containedfashion, substantially independently, using hardware, firmware and/orsoftware residing on the storage device itself. For instance, thestorage device may be capable of performing snapshot operations uponrequest, generally without intervention or oversight from any of theother components in the information management system 100. In thismanner, using hardware snapshots can off-load processing involved increating and management from other components in the system 100.

A “software” snapshot operation, on the other hand, can be a snapshotoperation in which one or more other components in the system (e.g., theclient computing devices 102, media agents 104, etc.) implement asoftware layer that manages the snapshot operation via interaction withthe target storage device. For instance, the component implementing thesnapshot management software layer may derive a set of pointers and/ordata that represents the snapshot. The snapshot management softwarelayer may then transmit the same to the target storage device, alongwith appropriate instructions for writing the snapshot.

Some types of snapshots do not actually create another physical copy ofall the data as it existed at the particular point in time, but maysimply create pointers that are able to map files and directories tospecific memory locations (e.g., disk blocks) where the data resides, asit existed at the particular point in time. For example, a snapshot copymay include a set of pointers derived from the file system or anapplication. In some other cases, the snapshot may created at theblock-level, such as where creation of the snapshot occurs withoutawareness of the file system. Each pointer points to a respective storeddata block, so collectively, the set of pointers reflect the storagelocation and state of the data object (e.g., file(s) or volume(s) ordata set(s)) at a particular point in time when the snapshot copy wascreated.

In some embodiments, once a snapshot has been taken, subsequent changesto the file system typically do not overwrite the blocks in use at thetime of the snapshot. Therefore, the initial snapshot may use only asmall amount of disk space needed to record a mapping or other datastructure representing or otherwise tracking the blocks that correspondto the current state of the file system. Additional disk space isusually required only when files and directories are actually modifiedlater. Furthermore, when files are modified, typically only the pointerswhich map to blocks are copied, not the blocks themselves. In someembodiments, for example in the case of “copy-on-write” snapshots, whena block changes in primary storage, the block is copied to secondarystorage or cached in primary storage before the block is overwritten inprimary storage. The snapshot mapping of file system data is alsoupdated to reflect the changed block(s) at that particular point intime. In some other cases, a snapshot includes a full physical copy ofall or substantially all of the data represented by the snapshot.Further examples of snapshot operations are provided in U.S. Pat. No.7,529,782, which is incorporated by reference herein.

A snapshot copy in many cases can be made quickly and withoutsignificantly impacting primary computing resources because largeamounts of data need not be copied or moved. In some embodiments, asnapshot may exist as a virtual file system, parallel to the actual filesystem. Users in some cases gain read-only access to the record of filesand directories of the snapshot. By electing to restore primary data 112from a snapshot taken at a given point in time, users may also returnthe current file system to the state of the file system that existedwhen the snapshot was taken.

Replication Operations

Another type of secondary copy operation is a replication operation.Some types of secondary copies 116 are used to periodically captureimages of primary data 112 at particular points in time (e.g., backups,archives, and snapshots). However, it can also be useful for recoverypurposes to protect primary data 112 in a more continuous fashion, byreplicating the primary data 112 substantially as changes occur. In somecases a replication copy can be a mirror copy, for instance, wherechanges made to primary data 112 are mirrored or substantiallyimmediately copied to another location (e.g., to secondary storagedevice(s) 108). By copying each write operation to the replication copy,two storage systems are kept synchronized or substantially synchronizedso that they are virtually identical at approximately the same time.Where entire disk volumes are mirrored, however, mirroring can requiresignificant amount of storage space and utilizes a large amount ofprocessing resources.

According to some embodiments storage operations are performed onreplicated data that represents a recoverable state, or “known goodstate” of a particular application running on the source system. Forinstance, in certain embodiments, known good replication copies may beviewed as copies of primary data 112. This feature allows the system todirectly access, copy, restore, backup or otherwise manipulate thereplication copies as if the data was the “live”, primary data 112. Thiscan reduce access time, storage utilization, and impact on sourceapplications 110, among other benefits.

Based on known good state information, the information management system100 can replicate sections of application data that represent arecoverable state rather than rote copying of blocks of data. Examplesof compatible replication operations (e.g., continuous data replication)are provided in U.S. Pat. No. 7,617,262, which is incorporated byreference herein.

Deduplication/Single-Instancing Operations

Another type of data movement operation is deduplication orsingle-instance storage, which is useful to reduce the amount of datawithin the system. For instance, some or all of the above-describedsecondary storage operations can involve deduplication in some fashion.New data is read, broken down into portions (e.g., sub-file levelblocks, files, etc.) of a selected granularity, compared with blocksthat are already stored, and only the new blocks are stored. Blocks thatalready exist are represented as pointers to the already stored data.

In order to streamline the comparison process, the informationmanagement system 100 may calculate and/or store signatures (e.g.,hashes) corresponding to the individual data blocks in a database andcompare the hashes instead of comparing entire data blocks. In somecases, only a single instance of each element is stored, anddeduplication operations may therefore be referred to interchangeably as“single-instancing” operations. Depending on the implementation,however, deduplication or single-instancing operations can store morethan one instance of certain data blocks, but nonetheless significantlyreduce data redundancy.

Depending on the embodiment, deduplication blocks can be of fixed orvariable length. Using variable length blocks can provide enhanceddeduplication by responding to changes in the data stream, but caninvolve complex processing. In some cases, the information managementsystem 100 utilizes a technique for dynamically aligning deduplicationblocks (e.g., fixed-length blocks) based on changing content in the datastream, as described in U.S. Pat. Pub. No. 2012/0084269, which isincorporated by reference herein.

The information management system 100 can perform deduplication in avariety of manners at a variety of locations in the informationmanagement system 100. For instance, in some embodiments, theinformation management system 100 implements “target-side” deduplicationby deduplicating data (e.g., secondary copies 116) stored in thesecondary storage devices 108. In some such cases, the media agents 144are generally configured to manage the deduplication process. Forinstance, one or more of the media agents 144 maintain a correspondingdeduplication database that stores deduplication information (e.g.,datablock signatures). Examples of such a configuration are provided inU.S. Pat. Pub. No. 2012/0150826, which is incorporated by referenceherein. Instead of or in combination with “target-side” deduplication,deduplication can also be performed on the “source-side” (or“client-side”), e.g., to reduce the amount of traffic between the mediaagents 144 and the client computing device(s) 102 and/or reduceredundant data stored in the primary storage devices 104. Examples ofsuch deduplication techniques are provided in U.S. Pat. Pub. No.2012/0150818, which is incorporated by reference herein.

Information Lifecycle Management and Hierarchical Storage ManagementOperations

In some embodiments, files and other data over their lifetime move frommore expensive, quick access storage to less expensive, slower accessstorage. Operations associated with moving data through various tiers ofstorage are sometimes referred to as information lifecycle management(ILM) operations.

One type of ILM operation is a hierarchical storage management (HSM)operation. A HSM operation is generally an operation for automaticallymoving data between classes of storage devices, such as betweenhigh-cost and low-cost storage devices. For instance, an HSM operationmay involve movement of data from primary storage devices 104 tosecondary storage devices 108, or between tiers of secondary storagedevices 108. With each tier, the storage devices may be progressivelyrelatively cheaper, have relatively slower access/restore times, etc.For example, movement of data between tiers may occur as data becomesless important over time.

In some embodiments, an HSM operation is similar to an archive operationin that creating an HSM copy may (though not always) involve deletingsome of the source data, e.g., according to one or more criteria relatedto the source data. For example, an HSM copy may include data fromprimary data 112 or a secondary copy 116 that is larger than a givensize threshold or older than a given age threshold and that is stored ina backup format.

Often, and unlike some types of archive copies, HSM data that is removedor aged from the source copy is replaced by a logical reference pointeror stub. The reference pointer or stub can be stored in the primarystorage device 104 (or other source storage device, such as a secondarystorage device 108) to replace the deleted data in primary data 112 (orother source copy) and to point to or otherwise indicate the newlocation in a secondary storage device 108.

According to one example, files are generally moved between higher andlower cost storage depending on how often the files are accessed. When auser requests access to the HSM data that has been removed or migrated,the information management system 100 uses the stub to locate the dataand often make recovery of the data appear transparent, even though theHSM data may be stored at a location different from the remaining sourcedata. In this manner, the data appears to the user (e.g., in file systembrowsing windows and the like) as if it still resides in the sourcelocation (e.g., in a primary storage device 104). The stub may alsoinclude some metadata associated with the corresponding data, so that afile system and/or application can provide some information about thedata object and/or a limited-functionality version (e.g., a preview) ofthe data object.

An HSM copy may be stored in a format other than the native applicationformat (e.g., where the data is compressed, encrypted, deduplicated,and/or otherwise modified from the original application format). In somecases, copies which involve the removal of data from source storage andthe maintenance of stub or other logical reference information on sourcestorage may be referred to generally as “on-line archive copies”. On theother hand, copies which involve the removal of data from source storagewithout the maintenance of stub or other logical reference informationon source storage may be referred to as “off-line archive copies”.Examples of HSM and ILM techniques are provided in U.S. Pat. No.7,343,453, which is incorporated by reference herein.

Auxiliary Copy and Disaster Recovery Operations

An auxiliary copy is generally a copy operation in which a copy iscreated of an existing secondary copy 116. For instance, an initial or“primary” secondary copy 116 may be generated using or otherwise bederived from primary data 112 (or other data residing in the secondarystorage subsystem 118), whereas an auxiliary copy is generated from theinitial secondary copy 116. Auxiliary copies can be used to createadditional standby copies of data and may reside on different secondarystorage devices 108 than initial secondary copies 116. Thus, auxiliarycopies can be used for recovery purposes if initial secondary copies 116become unavailable. Exemplary compatible auxiliary copy techniques aredescribed in further detail in U.S. Pat. No. 8,230,195, which isincorporated by reference herein.

The information management system 100 may also perform disaster recoveryoperations that make or retain disaster recovery copies, often assecondary, high-availability disk copies. The information managementsystem 100 may create secondary disk copies and store the copies atdisaster recovery locations using auxiliary copy or replicationoperations, such as continuous data replication technologies. Dependingon the particular data protection goals, disaster recovery locations canbe remote from the client computing devices 102 and primary storagedevices 104, remote from some or all of the secondary storage devices108, or both.

Data Analysis, Reporting, and Management Operations

Data analysis, reporting, and management operations can be differentthan data movement operations in that they do not necessarily involvethe copying, migration or other transfer of data (e.g., primary data 112or secondary copies 116) between different locations in the system. Forinstance, data analysis operations may involve processing (e.g., offlineprocessing) or modification of already stored primary data 112 and/orsecondary copies 116. However, in some embodiments data analysisoperations are performed in conjunction with data movement operations.Some data analysis operations include content indexing operations andclassification operations which can be useful in leveraging the dataunder management to provide enhanced search and other features. Otherdata analysis operations such as compression and encryption can providedata reduction and security benefits, respectively.

Classification Operations/Content Indexing

In some embodiments, the information management system 100 analyzes andindexes characteristics, content, and metadata associated with the datastored within the primary data 112 and/or secondary copies 116,providing enhanced search capabilities for data discovery and otherpurposes. The content indexing can be used to identify files or otherdata objects having pre-defined content (e.g., user-defined keywords orphrases), metadata (e.g., email metadata such as “to”, “from”, “cc”,“bcc”, attachment name, received time, etc.).

The information management system 100 generally organizes and cataloguesthe results in a content index, which may be stored within the mediaagent database 152, for example. The content index can also include thestorage locations of (or pointer references to) the indexed data in theprimary data 112 or secondary copies 116, as appropriate. The resultsmay also be stored, in the form of a content index database orotherwise, elsewhere in the information management system 100 (e.g., inthe primary storage devices 104, or in the secondary storage device108). Such index data provides the storage manager 140 or anothercomponent with an efficient mechanism for locating primary data 112and/or secondary copies 116 of data objects that match particularcriteria.

For instance, search criteria can be specified by a user through userinterface 158 of the storage manager 140. In some cases, the informationmanagement system 100 analyzes data and/or metadata in secondary copies116 to create an “off-line” content index, without significantlyimpacting the performance of the client computing devices 102. Dependingon the embodiment, the system can also implement “on-line” contentindexing, e.g., of primary data 112. Examples of compatible contentindexing techniques are provided in U.S. Pat. No. 8,170,995, which isincorporated by reference herein.

In order to leverage the data stored in the information managementsystem 100 to perform these and other tasks, one or more components canbe configured to scan data and/or associated metadata for classificationpurposes to populate a database of information (which can be referred toas a “metabase”). Such scanned, classified data and/or metadata may beincluded in a separate database and/or on a separate storage device fromprimary data 112 (and/or secondary copies 116), such that operationsrelated to the database do not significantly impact performance on othercomponents in the information management system 100.

In other cases, the database(s) may be stored along with primary data112 and/or secondary copies 116. Files or other data objects can beassociated with user-specified identifiers (e.g., tag entries) in themedia agent 144 (or other indices) to facilitate searches of stored dataobjects. Among a number of other benefits, the metabase can also allowefficient, automatic identification of files or other data objects toassociate with secondary copy or other information management operations(e.g., in lieu of scanning an entire file system). Examples ofcompatible metabases and data classification operations are provided inU.S. Pat. Nos. 8,229,954 and 7,747,579, which are incorporated byreference herein.

Encryption Operations

The information management system 100 in some cases is configured toprocess data (e.g., files or other data objects, secondary copies 116,etc.), according to an appropriate encryption algorithm (e.g., Blowfish,Advanced Encryption Standard [AES], Triple Data Encryption Standard[3-DES], etc.) to limit access and provide data security in theinformation management system 100.

The information management system 100 in some cases encrypts the data atthe client level, such that the client computing devices 102 (e.g., thedata agents 142) encrypt the data prior to forwarding the data to othercomponents, e.g., before sending the data media agents 144 during asecondary copy operation. In such cases, the client computing device 102may maintain or have access to an encryption key or passphrase fordecrypting the data upon restore. Encryption can also occur whencreating copies of secondary copies, e.g., when creating auxiliarycopies or archive copies. In yet further embodiments, the secondarystorage devices 108 can implement built-in, high performance hardwareencryption.

Management and Reporting Operations

Certain embodiments leverage the integrated, ubiquitous nature of theinformation management system 100 to provide useful system-widemanagement and reporting functions. Examples of some compatiblemanagement and reporting techniques are provided in U.S. Pat. No.7,343,453, entitled “HIERARCHICAL SYSTEMS AND METHODS FOR PROVIDING AUNIFIED VIEW OF STORAGE INFORMATION”, which is incorporated by referenceherein.

Operations management can generally include monitoring and managing thehealth and performance of information management system 100 by, withoutlimitation, performing error tracking, generating granularstorage/performance metrics (e.g., job success/failure information,deduplication efficiency, etc.), generating storage modeling and costinginformation, and the like.

As an example, a storage manager 140 or other component in theinformation management system 100 may analyze traffic patterns andsuggest or automatically route data via a particular route to e.g.,certain facilitate storage and minimize congestion. In some embodiments,the system can generate predictions relating to storage operations orstorage operation information. Such predictions described may be basedon a trending analysis that may be used to predict various networkoperations or use of network resources such as network traffic levels,storage media use, use of bandwidth of communication links, use of mediaagent components, etc. Further examples of traffic analysis, trendanalysis, prediction generation, and the like are described in U.S. Pat.No. 7,343,453, which is incorporated by reference herein.

In some configurations, a master storage manager 140 may track thestatus of a set of associated storage operation cells in a hierarchy ofinformation management cells, such as the status of jobs, systemcomponents, system resources, and other items, by communicating withstorage managers 140 (or other components) in the respective storageoperation cells. Moreover, the master storage manager 140 may track thestatus of its associated storage operation cells and associatedinformation management operations by receiving periodic status updatesfrom the storage managers 140 (or other components) in the respectivecells regarding jobs, system components, system resources, and otheritems. In some embodiments, a master storage manager 140 may storestatus information and other information regarding its associatedstorage operation cells and other system information in its index 150(or other location).

The master storage manager or other component in the system may alsodetermine whether a storage-related criteria or other criteria issatisfied, and perform an action or trigger event (e.g., data migration)in response to the criteria being satisfied, such as where a storagethreshold is met for a particular volume, or where inadequate protectionexists for certain data. For instance, in some embodiments, the systemuses data from one or more storage operation cells to advise users ofrisks or indicates actions that can be used to mitigate or otherwiseminimize these risks, and in some embodiments, dynamically takes actionto mitigate or minimize these risks. For example, an informationmanagement policy may specify certain requirements (e.g., that a storagedevice should maintain a certain amount of free space, that secondarycopies should occur at a particular interval, that data should be agedand migrated to other storage after a particular period, that data on asecondary volume should always have a certain level of availability andbe able to be restored within a given time period, that data on asecondary volume may be mirrored or otherwise migrated to a specifiednumber of other volumes, etc.). If a risk condition or other criteria istriggered, the system can notify the user of these conditions and maysuggest (or automatically implement) an action to mitigate or otherwiseaddress the condition or minimize risk. For example, the system mayindicate that data from a primary copy 112 should be migrated to asecondary storage device 108 to free space on the primary storage device104. Examples of the use of risk factors and other triggering criteriaare described in U.S. Pat. No. 7,343,453, which is incorporated byreference herein.

In some embodiments, the system 100 may also determine whether a metricor other indication satisfies a particular storage criteria and, if so,perform an action. For example, as previously described, a storagepolicy or other definition might indicate that a storage manager 140should initiate a particular action if a storage metric or otherindication drops below or otherwise fails to satisfy a specifiedcriteria such as a threshold of data protection. Examples of suchmetrics are described in U.S. Pat. No. 7,343,453, which is incorporatedby reference herein.

In some embodiments, risk factors may be quantified into certainmeasurable service or risk levels for ease of comprehension. Forexample, certain applications and associated data may be considered tobe more important by an enterprise than other data and services.Financial compliance data, for example, may be of greater importancethan marketing materials, etc. Network administrators may assignpriorities or “weights” to certain data or applications, correspondingto its importance (priority value). The level of compliance with thestorage operations specified for these applications may also be assigneda certain value. Thus, the health, impact and overall importance of aservice on an enterprise may be determined, for example, by measuringthe compliance value and calculating the product of the priority valueand the compliance value to determine the “service level” and comparingit to certain operational thresholds to determine if the operation isbeing performed within a specified data protection service level.Further examples of the service level determination are provided in U.S.Pat. No. 7,343,453, which is incorporated by reference herein.

The system 100 may additionally calculate data costing and dataavailability associated with information management operation cellsaccording to an embodiment of the invention. For instance, data receivedfrom the cell may be used in conjunction with hardware-relatedinformation and other information about network elements to generateindications of costs associated with storage of particular data in thesystem or the availability of particular data in the system. In general,components in the system are identified and associated information isobtained (dynamically or manually). Characteristics or metricsassociated with the network elements may be identified and associatedwith that component element for further use generating an indication ofstorage cost or data availability. Exemplary information generated couldinclude how fast a particular department is using up available storagespace, how long data would take to recover over a particular networkpathway from a particular secondary storage device, costs over time,etc. Moreover, in some embodiments, such information may be used todetermine or predict the overall cost associated with the storage ofcertain information. The cost associated with hosting a certainapplication may be based, at least in part, on the type of media onwhich the data resides. Storage devices may be assigned to a particularcost category which is indicative of the cost of storing information onthat device. Further examples of costing techniques are described inU.S. Pat. No. 7,343,453, which is incorporated by reference herein.

Any of the above types of information (e.g., information related totrending, predictions, job, cell or component status, risk, servicelevel, costing, etc.) can generally be provided to users via the userinterface 158 in a single, integrated view or console. The console maysupport a reporting capability that allows for the generation of avariety of reports, which may be tailored to a particular aspect ofinformation management. Report types may include: scheduling, eventmanagement, media management and data aging. Available reports may alsoinclude backup history, data aging history, auxiliary copy history, jobhistory, library and drive, media in library, restore history andstorage policy. Such reports may be specified and created at a certainpoint in time as a network analysis, forecasting, or provisioning tool.Integrated reports may also be generated that illustrate storage andperformance metrics, risks and storage costing information. Moreover,users may create their own reports based on specific needs.

The integrated user interface 158 can include an option to show a“virtual view” of the system that graphically depicts the variouscomponents in the system using appropriate icons. As one example, theuser interface may provide a graphical depiction of one or more primarystorage devices 104, the secondary storage devices 108, data agents 142and/or media agents 144, and their relationship to one another in theinformation management system 100. The operations managementfunctionality can facilitate planning and decision-making. For example,in some embodiments, a user may view the status of some or all jobs aswell as the status of each component of the information managementsystem 100. Users may then plan and make decisions based on this data.For instance, a user may view high-level information regarding storageoperations for the information management system 100, such as jobstatus, component status, resource status (e.g., network pathways,etc.), and other information. The user may also drill down or use othermeans to obtain more detailed information regarding a particularcomponent, job, or the like.

Further examples of some reporting techniques and associated interfacesproviding an integrated view of an information management system areprovided in U.S. Pat. No. 7,343,453, which is incorporated by referenceherein.

The information management system 100 can also be configured to performsystem-wide e-discovery operations in some embodiments. In general,e-discovery operations provide a unified collection and searchcapability for data in the system, such as data stored in the secondarystorage devices 108 (e.g., backups, archives, or other secondary copies116). For example, the information management system 100 may constructand maintain a virtual repository for data stored in the informationmanagement system 100 that is integrated across source applications 110,different storage device types, etc. According to some embodiments,e-discovery utilizes other techniques described herein, such as dataclassification and/or content indexing.

Information Management Policies

As indicated previously, an information management policy 148 caninclude a data structure or other information source that specifies aset of parameters (e.g., criteria and rules) associated with secondarycopy or other information management operations.

One type of information management policy 148 is a storage policy.According to certain embodiments, a storage policy generally comprises adata structure or other information source that defines (or includesinformation sufficient to determine) a set of preferences or othercriteria for performing information management operations. Storagepolicies can include one or more of the following items: (1) what datawill be associated with the storage policy; (2) a destination to whichthe data will be stored; (3) datapath information specifying how thedata will be communicated to the destination; (4) the type of storageoperation to be performed; and (5) retention information specifying howlong the data will be retained at the destination.

As an illustrative example, data associated with a storage policy can belogically organized into groups. In some cases, these logical groupingscan be referred to as “sub-clients”. A sub-client may represent staticor dynamic associations of portions of a data volume. Sub-clients mayrepresent mutually exclusive portions. Thus, in certain embodiments, aportion of data may be given a label and the association is stored as astatic entity in an index, database or other storage location.

Sub-clients may also be used as an effective administrative scheme oforganizing data according to data type, department within theenterprise, storage preferences, or the like. Depending on theconfiguration, sub-clients can correspond to files, folders, virtualmachines, databases, etc. In one exemplary scenario, an administratormay find it preferable to separate e-mail data from financial data usingtwo different sub-clients.

A storage policy can define where data is stored by specifying a targetor destination storage device (or group of storage devices). Forinstance, where the secondary storage device 108 includes a group ofdisk libraries, the storage policy may specify a particular disk libraryfor storing the sub-clients associated with the policy. As anotherexample, where the secondary storage devices 108 include one or moretape libraries, the storage policy may specify a particular tape libraryfor storing the sub-clients associated with the storage policy, and mayalso specify a drive pool and a tape pool defining a group of tapedrives and a group of tapes, respectively, for use in storing thesub-client data. While information in the storage policy can bestatically assigned in some cases, some or all of the information in thestorage policy can also be dynamically determined based on criteria,which can be set forth in the storage policy. For instance, based onsuch criteria, a particular destination storage device(s) (or otherparameter of the storage policy) may be determined based oncharacteristics associated with the data involved in a particularstorage operation, device availability (e.g., availability of asecondary storage device 108 or a media agent 144), network status andconditions (e.g., identified bottlenecks), user credentials, and thelike)

Datapath information can also be included in the storage policy. Forinstance, the storage policy may specify network pathways and componentsto utilize when moving the data to the destination storage device(s). Insome embodiments, the storage policy specifies one or more media agents144 for conveying data (e.g., one or more sub-clients) associated withthe storage policy between the source (e.g., one or more host clientcomputing devices 102) and destination (e.g., a particular targetsecondary storage device 108).

A storage policy can also specify the type(s) of operations associatedwith the storage policy, such as a backup, archive, snapshot, auxiliarycopy, or the like. Retention information can specify how long the datawill be kept, depending on organizational needs (e.g., a number of days,months, years, etc.)

The information management policies 148 may also include one or morescheduling policies specifying when and how often to perform operations.Scheduling information may specify with what frequency (e.g., hourly,weekly, daily, event-based, etc.) or under what triggering conditionssecondary copy or other information management operations will takeplace. Scheduling policies in some cases are associated with particularcomponents, such as particular logical groupings of data associated witha storage policy (e.g., a sub-client), client computing device 102, andthe like. In one configuration, a separate scheduling policy ismaintained for particular logical groupings of data on a clientcomputing device 102. The scheduling policy specifies that those logicalgroupings are to be moved to secondary storage devices 108 every houraccording to storage policies associated with the respectivesub-clients.

When adding a new client computing device 102, administrators canmanually configure information management policies 148 and/or othersettings, e.g., via the user interface 158. However, this can be aninvolved process resulting in delays, and it may be desirable to begindata protecting operations quickly.

Thus, in some embodiments, the information management system 100automatically applies a default configuration to client computing device102. As one example, when one or more data agent(s) 142 are installed onone or more client computing devices 102, the installation script mayregister the client computing device 102 with the storage manager 140,which in turn applies the default configuration to the new clientcomputing device 102. In this manner, data protection operations canbegin substantially immediately. The default configuration can include adefault storage policy, for example, and can specify any appropriateinformation sufficient to begin data protection operations. This caninclude a type of data protection operation, scheduling information, atarget secondary storage device 108, data path information (e.g., aparticular media agent 144), and the like.

Other types of information management policies 148 are possible. Forinstance, the information management policies 148 can also include oneor more audit or security policies. An audit policy is a set ofpreferences, rules and/or criteria that protect sensitive data in theinformation management system 100. For example, an audit policy maydefine “sensitive objects” as files or objects that contain particularkeywords (e.g. “confidential,” or “privileged”) and/or are associatedwith particular keywords (e.g., in metadata) or particular flags (e.g.,in metadata identifying a document or email as personal, confidential,etc.).

An audit policy may further specify rules for handling sensitiveobjects. As an example, an audit policy may require that a reviewerapprove the transfer of any sensitive objects to a cloud storage site,and that if approval is denied for a particular sensitive object, thesensitive object should be transferred to a local storage device 104instead. To facilitate this approval, the audit policy may furtherspecify how a secondary storage computing device 106 or other systemcomponent should notify a reviewer that a sensitive object is slated fortransfer.

In some implementations, the information management policies 148 mayinclude one or more provisioning policies. A provisioning policy caninclude a set of preferences, priorities, rules, and/or criteria thatspecify how clients 102 (or groups thereof) may utilize systemresources, such as available storage on cloud storage and/or networkbandwidth. A provisioning policy specifies, for example, data quotas forparticular client computing devices 102 (e.g. a number of gigabytes thatcan be stored monthly, quarterly or annually). The storage manager 140or other components may enforce the provisioning policy. For instance,the media agents 144 may enforce the policy when transferring data tosecondary storage devices 108. If a client computing device 102 exceedsa quota, a budget for the client computing device 102 (or associateddepartment) is adjusted accordingly or an alert may trigger.

While the above types of information management policies 148 have beendescribed as separate policies, one or more of these can be generallycombined into a single information management policy 148. For instance,a storage policy may also include or otherwise be associated with one ormore scheduling, audit, or provisioning policies. Moreover, whilestorage policies are typically associated with moving and storing data,other policies may be associated with other types of informationmanagement operations. The following is a non-exhaustive list of itemsthe information management policies 148 may specify:

-   -   schedules or other timing information, e.g., specifying when        and/or how often to perform information management operations;    -   the type of copy 116 (e.g., type of secondary copy) and/or copy        (e.g., type of secondary copy) format (e.g., snapshot, backup,        archive, HSM, etc.);    -   a location or a class or quality of storage for storing        secondary copies 116 (e.g., one or more particular secondary        storage devices 108);    -   preferences regarding whether and how to encrypt, compress,        deduplicate, or otherwise modify or transform secondary copies        116;    -   which system components and/or network pathways (e.g., preferred        media agents 144) should be used to perform secondary storage        operations;    -   resource allocation between different computing devices or other        system components used in performing information management        operations (e.g., bandwidth allocation, available storage        capacity, etc.);    -   whether and how to synchronize or otherwise distribute files or        other data objects across multiple computing devices or hosted        services; and    -   retention information specifying the length of time primary data        112 and/or secondary copies 116 should be retained, e.g., in a        particular class or tier of storage devices, or within the        information management system 100.

Policies can additionally specify or depend on a variety of historicalor current criteria that may be used to determine which rules to applyto a particular data object, system component, or information managementoperation, such as:

-   -   frequency with which primary data 112 or a secondary copy 116 of        a data object or metadata has been or is predicted to be used,        accessed, or modified;    -   time-related factors (e.g., aging information such as time since        the creation or modification of a data object);    -   deduplication information (e.g., hashes, data blocks,        deduplication block size, deduplication efficiency or other        metrics);    -   an estimated or historic usage or cost associated with different        components (e.g., with secondary storage devices 108);    -   the identity of users, applications 110, client computing        devices 102 and/or other computing devices that created,        accessed, modified, or otherwise utilized primary data 112 or        secondary copies 116;    -   a relative sensitivity (e.g., confidentiality) of a data object,        e.g., as determined by its content and/or metadata;    -   the current or historical storage capacity of various storage        devices;    -   the current or historical network capacity of network pathways        connecting various components within the storage operation cell;    -   access control lists or other security information; and    -   the content of a particular data object (e.g., its textual        content) or of metadata associated with the data object.        Exemplary Storage Policy and Secondary Storage Operations

FIG. 1E shows a data flow data diagram depicting performance of storageoperations by an embodiment of an information management system 100,according to an exemplary data storage policy 148A. The informationmanagement system 100 includes a storage manger 140, a client computingdevice 102 having a file system data agent 142A and an email data agent142B residing thereon, a primary storage device 104, two media agents144A, 144B, and two secondary storage devices 108A, 108B: a disk library108A and a tape library 108B. As shown, the primary storage device 104includes primary data 112A, 112B associated with a logical grouping ofdata associated with a file system) and a logical grouping of dataassociated with email data, respectively. Although for simplicity thelogical grouping of data associated with the file system is referred toas a file system sub-client, and the logical grouping of data associatedwith the email data is referred to as an email sub-client, thetechniques described with respect to FIG. 1E can be utilized inconjunction with data that is organized in a variety of other manners.

As indicated by the dashed box, the second media agent 144B and the tapelibrary 108B are “off-site”, and may therefore be remotely located fromthe other components in the information management system 100 (e.g., ina different city, office building, etc.). In this manner, informationstored on the tape library 108B may provide protection in the event of adisaster or other failure.

The file system sub-client and its associated primary data 112A incertain embodiments generally comprise information generated by the filesystem and/or operating system of the client computing device 102, andcan include, for example, file system data (e.g., regular files, filetables, mount points, etc.), operating system data (e.g., registries,event logs, etc.), and the like. The e-mail sub-client, on the otherhand, and its associated primary data 112B, include data generated by ane-mail client application operating on the client computing device 102,and can include mailbox information, folder information, emails,attachments, associated database information, and the like. As describedabove, the sub-clients can be logical containers, and the data includedin the corresponding primary data 112A, 1128 may or may not be storedcontiguously.

The exemplary storage policy 148A includes backup copy preferences orrule set 160, disaster recovery copy preferences rule set 162, andcompliance copy preferences or rule set 164. The backup copy rule set160 specifies that it is associated with a file system sub-client 166and an email sub-client 168. Each of these sub-clients 166, 168 areassociated with the particular client computing device 102. The backupcopy rule set 160 further specifies that the backup operation will bewritten to the disk library 108A, and designates a particular mediaagent 144A to convey the data to the disk library 108A. Finally, thebackup copy rule set 160 specifies that backup copies created accordingto the rule set 160 are scheduled to be generated on an hourly basis andto be retained for 30 days. In some other embodiments, schedulinginformation is not included in the storage policy 148A, and is insteadspecified by a separate scheduling policy.

The disaster recovery copy rule set 162 is associated with the same twosub-clients 166, 168. However, the disaster recovery copy rule set 162is associated with the tape library 108B, unlike the backup copy ruleset 160. Moreover, the disaster recovery copy rule set 162 specifiesthat a different media agent 144B than the media agent 144A associatedwith the backup copy rule set 160 will be used to convey the data to thetape library 108B. As indicated, disaster recovery copies createdaccording to the rule set 162 will be retained for 60 days, and will begenerated on a daily basis. Disaster recovery copies generated accordingto the disaster recovery copy rule set 162 can provide protection in theevent of a disaster or other data-loss event that would affect thebackup copy 116A maintained on the disk library 108A.

The compliance copy rule set 164 is only associated with the emailsub-client 166, and not the file system sub-client 168. Compliancecopies generated according to the compliance copy rule set 164 willtherefore not include primary data 112A from the file system sub-client166. For instance, the organization may be under an obligation to storemaintain copies of email data for a particular period of time (e.g., 10years) to comply with state or federal regulations, while similarregulations do not apply to the file system data. The compliance copyrule set 164 is associated with the same tape library 108B and mediaagent 144B as the disaster recovery copy rule set 162, although adifferent storage device or media agent could be used in otherembodiments. Finally, the compliance copy rule set 164 specifies thatcopies generated under the compliance copy rule set 164 will be retainedfor 10 years, and will be generated on a quarterly basis.

At step 1, the storage manager 140 initiates a backup operationaccording to the backup copy rule set 160. For instance, a schedulingservice running on the storage manager 140 accesses schedulinginformation from the backup copy rule set 160 or a separate schedulingpolicy associated with the client computing device 102, and initiates abackup copy operation on an hourly basis. Thus, at the scheduled timeslot the storage manager 140 sends instructions to the client computingdevice 102 to begin the backup operation.

At step 2, the file system data agent 142A and the email data agent 142Bresiding on the client computing device 102 respond to the instructionsreceived from the storage manager 140 by accessing and processing theprimary data 112A, 112B involved in the copy operation from the primarystorage device 104. Because the operation is a backup copy operation,the data agent(s) 142A, 142B may format the data into a backup format orotherwise process the data.

At step 3, the client computing device 102 communicates the retrieved,processed data to the first media agent 144A, as directed by the storagemanager 140, according to the backup copy rule set 160. In some otherembodiments, the information management system 100 may implement aload-balancing, availability-based, or other appropriate algorithm toselect from the available set of media agents 144A, 144B. Regardless ofthe manner the media agent 144A is selected, the storage manager 140 mayfurther keep a record in the storage manager database 140 of theassociation between the selected media agent 144A and the clientcomputing device 102 and/or between the selected media agent 144A andthe backup copy 116A.

The target media agent 144A receives the data from the client computingdevice 102, and at step 4 conveys the data to the disk library 108A tocreate the backup copy 116A, again at the direction of the storagemanager 140 and according to the backup copy rule set 160. The secondarystorage device 108A can be selected in other ways. For instance, themedia agent 144A may have a dedicated association with a particularsecondary storage device(s), or the storage manager 140 or media agent144A may select from a plurality of secondary storage devices, e.g.,according to availability, using one of the techniques described in U.S.Pat. No. 7,246,207, which is incorporated by reference herein.

The media agent 144A can also update its index 153 to include dataand/or metadata related to the backup copy 116A, such as informationindicating where the backup copy 116A resides on the disk library 108A,data and metadata for cache retrieval, etc. After the 30 day retentionperiod expires, the storage manager 140 instructs the media agent 144Ato delete the backup copy 116A from the disk library 108A. The storagemanager 140 may similarly update its index 150 to include informationrelating to the storage operation, such as information relating to thetype of storage operation, a physical location associated with one ormore copies created by the storage operation, the time the storageoperation was performed, status information relating to the storageoperation, the components involved in the storage operation, and thelike. In some cases, the storage manager 140 may update its index 150 toinclude some or all of the information stored in the index 153 of themedia agent 144A.

At step 5, the storage manager 140 initiates the creation of a disasterrecovery copy 1168 according to the disaster recovery copy rule set 162.For instance, at step 6, based on instructions received from the storagemanager 140 at step 5, the specified media agent 144B retrieves the mostrecent backup copy 116A from the disk library 108A.

At step 7, again at the direction of the storage manager 140 and asspecified in the disaster recovery copy rule set 162, the media agent144B uses the retrieved data to create a disaster recovery copy 1168 onthe tape library 1088. In some cases, the disaster recovery copy 1168 isa direct, mirror copy of the backup copy 116A, and remains in the backupformat. In other embodiments, the disaster recovery copy 116C may begenerated in some other manner, such as by using the primary data 112A,1128 from the storage device 104 as source data. The disaster recoverycopy operation is initiated once a day and the disaster recovery copies116A are deleted after 60 days.

At step 8, the storage manager 140 initiates the creation of acompliance copy 116C, according to the compliance copy rule set 164. Forinstance, the storage manager 140 instructs the media agent 144B tocreate the compliance copy 116C on the tape library 108B at step 9, asspecified in the compliance copy rule set 164. In the example, thecompliance copy 116C is generated using the disaster recovery copy 116B.In other embodiments, the compliance copy 116C is instead generatedusing either the primary data 112B corresponding to the email sub-clientor using the backup copy 116A from the disk library 108A as source data.As specified, in the illustrated example, compliance copies 116C arecreated quarterly, and are deleted after ten years.

While not shown in FIG. 1E, at some later point in time, a restoreoperation can be initiated involving one or more of the secondary copies116A, 1168, 116C. As one example, a user may manually initiate a restoreof the backup copy 116A by interacting with the user interface 158 ofthe storage manager 140. The storage manager 140 then accesses data inits index 150 (and/or the respective storage policy 148A) associatedwith the selected backup copy 116A to identify the appropriate mediaagent 144A and/or secondary storage device 116A.

In other cases, a media agent may be selected for use in the restoreoperation based on a load balancing algorithm, an availability basedalgorithm, or other criteria. The selected media agent 144A retrievesthe data from the disk library 108A. For instance, the media agent 144Amay access its index 153 to identify a location of the backup copy 116Aon the disk library 108A, or may access location information residing onthe disk 108A itself.

When the backup copy 116A was recently created or accessed, the mediaagent 144A accesses a cached version of the backup copy 116A residing inthe media agent index 153, without having to access the disk library108A for some or all of the data. Once it has retrieved the backup copy116A, the media agent 144A communicates the data to the source clientcomputing device 102. Upon receipt, the file system data agent 142A andthe email data agent 142B may unpackage (e.g., restore from a backupformat to the native application format) the data in the backup copy116A and restore the unpackaged data to the primary storage device 104.

Exemplary Secondary Copy Formatting

The formatting and structure of secondary copies 116 can vary, dependingon the embodiment. In some cases, secondary copies 116 are formatted asa series of logical data units or “chunks” (e.g., 512 MB, 1 GB, 2 GB, 4GB, or 8 GB chunks). This can facilitate efficient communication andwriting to secondary storage devices 108, e.g., according to resourceavailability. For example, a single secondary copy 116 may be written ona chunk-by-chunk basis to a single secondary storage device 108 oracross multiple secondary storage devices 108. In some cases, users canselect different chunk sizes, e.g., to improve throughput to tapestorage devices.

Generally, each chunk can include a header and a payload. The payloadcan include files (or other data units) or subsets thereof included inthe chunk, whereas the chunk header generally includes metadata relatingto the chunk, some or all of which may be derived from the payload. Forexample, during a secondary copy operation, the media agent 144, storagemanager 140, or other component may divide the associated files intochunks and generate headers for each chunk by processing the constituentfiles.

The headers can include a variety of information such as fileidentifier(s), volume(s), offset(s), or other information associatedwith the payload data items, a chunk sequence number, etc. Importantly,in addition to being stored with the secondary copy 116 on the secondarystorage device 108, the chunk headers can also be stored to the index153 of the associated media agent(s) 144 and/or the storage managerindex 150. This is useful in some cases for providing faster processingof secondary copies 116 during restores or other operations. In somecases, once a chunk is successfully transferred to a secondary storagedevice 108, the secondary storage device 108 returns an indication ofreceipt, e.g., to the media agent 144 and/or storage manager 140, whichmay update their respective indexes 150, 153 accordingly. Duringrestore, chunks may be processed (e.g., by the media agent 144)according to the information in the chunk header to reassemble thefiles.

Data can also be communicated within the information management system100 in data channels that connect the client computing devices 102 tothe secondary storage devices 108. These data channels can be referredto as “data streams”, and multiple data streams can be employed toparallelize an information management operation, improving data transferrate, among providing other advantages. Example data formattingtechniques including techniques involving data streaming, chunking, andthe use of other data structures in creating copies (e.g., secondarycopies) are described in U.S. Pat. Nos. 7,315,923 and 8,156,086, andU.S. Pat. Pub. No. 2010-0299490, each of which is incorporated byreference herein.

FIGS. 1F and 1G are diagrams of example data streams 170 and 171,respectively, that may be employed for performing data storageoperations. Referring to FIG. 1F, the data agent 142 forms the datastream 170 from the data associated with a client 102 (e.g., primarydata 112). The data stream 170 is composed of multiple pairs of streamheader 172 and stream payload 174. The data streams 170 and 171 shown inthe illustrated example are for a single-instanced storage operation,and a stream payload 174 therefore includes both single-instance (“SI”)data and/or non-SI data. A stream header 172 includes metadata about thestream payload 174. This metadata may include, for example, a length ofthe stream payload 174, an indication of whether the stream payload 174is encrypted, an indication of whether the stream payload 174 iscompressed, an archive file identifier (ID), an indication of whetherthe stream payload 174 is single instanceable, and an indication ofwhether the stream payload 174 is a start of a block of data.

Referring to FIG. 1G, the data stream 171 has the stream header 172 andstream payload 174 aligned into multiple data blocks. In this example,the data blocks are of size 64 Kb. The first two stream header 172 andstream payload 174 pairs comprise a first data block of size 64 Kb. Thefirst stream header 172 indicates that the length of the succeedingstream payload 174 is 63 Kb and that it is the start of a data block.The next stream header 172 indicates that the succeeding stream payload174 has a length of 1 Kb and that it is not the start of a new datablock. Immediately following stream payload 174 are an identifier header176 and identifier data 178 pair. The identifier header 176 includes anindication that the succeeding identifier data 178 includes theidentifier for the immediately previous data block. The identifier data178 includes the identifier that the data agent 142 generated for thedata block. The data stream 171 also includes other stream header 172and stream payload 174 pairs, which may be for SI data and/or for non-SIdata.

FIG. 1H is a diagram illustrating the data structures 180 that may beused to store blocks of SI data and non-SI data on the storage device(e.g., secondary storage device 108). According to certain embodiments,the data structures 180 do not form part of a native file system of thestorage device. The data structures 180 include one or more volumefolders 182, one or more chunk folders 184/185 within a volume folder182, and multiple files within a chunk folder 184. Each chunk folder184/185 includes a metadata file 186/187, a metadata index file 188/189,one or more container files 190/191/193, and a container index file192/194. The metadata file 186/187 stores non-SI data blocks as well aslinks to SI data blocks stored in container files. The metadata indexfile 188/189 stores an index to the data in the metadata file 186/187.The container files 190/191/193 store SI data blocks. The containerindex file 192/194 stores an index to the container files 190/191/193.Among other things, the container index file 192/194 stores anindication of whether a corresponding block in a container file190/191/193 is referred to by a link in a metadata file 186/187. Forexample, data block B2 in the container file 190 is referred to by alink in the metadata file 187 in the chunk folder 185. Accordingly, thecorresponding index entry in the container index file 192 indicates thatthe data block B2 in the container file 190 is referred to. As anotherexample, data block B1 in the container file 191 is referred to by alink in the metadata file 187, and so the corresponding index entry inthe container index file 192 indicates that this data block is referredto.

As an example, the data structures 180 illustrated in FIG. 7 may havebeen created as a result of two storage operations involving two clients102. For example, a first storage operation on a first client 102 couldresult in the creation of the first chunk folder 184, and a secondstorage operation on a second client 102 could result in the creation ofthe second chunk folder 185. The container files 190/191 in the firstchunk folder 184 would contain the blocks of SI data of the first client102. If the two clients 102 have substantially similar data, the secondstorage operation on the data of the second client 102 would result inthe media agent 144 storing primarily links to the data blocks of thefirst client 102 that are already stored in the container files 190/191.Accordingly, while a first storage operation may result in storingnearly all of the data subject to the storage operation, subsequentstorage operations involving similar data may result in substantial datastorage space savings, because links to already stored data blocks canbe stored instead of additional instances of data blocks.

If the operating system of the secondary storage computing device 106 onwhich the media agent 144 resides supports sparse files, then when themedia agent 144 creates container files 190/191/193, it can create themas sparse files. As previously described, a sparse file is type of filethat may include empty space (e.g., a sparse file may have real datawithin it, such as at the beginning of the file and/or at the end of thefile, but may also have empty space in it that is not storing actualdata, such as a contiguous range of bytes all having a value of zero).Having the container files 190/191/193 be sparse files allows the mediaagent 144 to free up space in the container files 190/191/193 whenblocks of data in the container files 190/191/193 no longer need to bestored on the storage devices. In some examples, the media agent 144creates a new container file 190/191/193 when a container file190/191/193 either includes 100 blocks of data or when the size of thecontainer file 190 exceeds 50 Mb. In other examples, the media agent 144creates a new container file 190/191/193 when a container file190/191/193 satisfies other criteria (e.g., it contains fromapproximately 100 to approximately 1000 blocks or when its size exceedsapproximately 50 Mb to 1 Gb).

In some cases, a file on which a storage operation is performed maycomprise a large number of data blocks. For example, a 100 Mb file maybe comprised in 400 data blocks of size 256 Kb. If such a file is to bestored, its data blocks may span more than one container file, or evenmore than one chunk folder. As another example, a database file of 20 Gbmay comprise over 40,000 data blocks of size 512 Kb. If such a databasefile is to be stored, its data blocks will likely span multiplecontainer files, multiple chunk folders, and potentially multiple volumefolders. As described in detail herein, restoring such files may thusrequiring accessing multiple container files, chunk folders, and/orvolume folders to obtain the requisite data blocks.

Example High Availability Deduplication System

As shown in FIG. 2A, the system 100 can further include one or morededuplication database media agents 202-208 (DDB media agents), examplesof which are described in greater detail in U.S. Pub. No. 2012/0150826,previously incorporated herein by reference. The DDB media agents202-208 can include deduplication databases 210A-210D that storededuplication information, such as data block signatures and thelocation information of data blocks stored in the secondary storagedevices 108, as described above. The deduplication databases 210A-210Dcan also store other deduplication information, such as a count valueindicative of the number of instances that a particular block is used.Furthermore, the DDB media agents 202-208 can be implemented on the samecomputing devices 106 as one or more of the media agents 144, or onseparate computing devices 106.

During a backup or other secondary copy operation using deduplicationtechniques, the system 100 can query the DDB media agents 202-208 forsignatures of the data blocks to be backed up. In some embodiments, theclient computing device 102 can query the DDB media agents 202-208 andin certain embodiments, the secondary storage computing devices 106 canquery the DDB media agents 202-208. When a signature is found in the DDBmedia agents 202-208, a link to the location of a copy of the data blockstored in the secondary storage devices 108 is stored as part of thebackup. When a signature is not found in the DDB media agents 202-208, acopy of the data block is stored in the secondary storage devices 108,and the signature of the data block is stored in the DDB media agents.

A data block distribution policy can specify which DDB media agents202-208 store which signatures and which DDB media agents 202-208 aretherefore queried for particular data block signatures. For example, thedistribution policy can indicate that data block signatures are storedin DDB media agents 202-208 based on a modulo operation of the signatureof the data block, as described previously. Furthermore, should one ofthe DDB media agents (e.g., DDB media agent 202) become unavailable, thedistribution policy can specify another DDB media agent (e.g., DDB mediaagent 206) as a failover DDB media agent and use the failover DDB mediaagent for deduplication operations while the other DDB media agent (DDBmedia agent 202) is unavailable.

FIG. 2B is a block diagram illustrative of an embodiment of failoverpolicy or scheme for deduplication database media agents 202-208. Asdescribed previously, in some embodiments, DDB media agents 202-208 canbecome unavailable due to a network outage, power outage,hardware/software malfunction, scheduled maintenance, etc. When a DDBmedia agent becomes unavailable, a failover DDB media agent can be usedin its place.

In the illustrated embodiment of FIG. 2B, four DDB media agents (DDBmedia agent 202, DDB media agent 204, DDB media agent 206, DDB mediaagent 208) are implemented as failover DDB media agents in a round robinfashion, such that each DDB media agent is configured as a failover DDBmedia agent for another DDB media agent, e.g., DDB media agent 202 isthe failover DDB media agent for DDB media agent 208, DDB media agent204 is the failover DDB media agent for DDB media agent 202, DDB mediaagent 206 is the failover DDB media agent for DDB media agent 204, andDDB media agent 208 is the failover DDB media agent for DDB media agent206. In this way, should any one of the DDB media agents becomeunavailable, its assigned failover DDB media agent will handle anyadditional queries. Furthermore, should all but one DDB media agentbecome unavailable, the remaining DDB media agent can satisfy thesignature queries for the other DDB media agents.

It will be understood that other techniques can be used to implement thefailover policy. For example, one of the DDB media agents can beidentified as the failover DDB media agent for multiple DDB mediaagents. Alternatively, one DDB media agent can remain in a stand-by modeand can be activated when another one of the DDB media agents becomesunavailable.

In some embodiments, when one of the DDB media agents becomesunavailable, the signature function can be altered such that signaturesthat are assigned to be stored by the unavailable DDB media agent areevenly distributed amongst the other DDB media agents. As a non-limitingexample, modulo four can be used to evenly distribute signatures betweenfour DDB media agents. If the third DDB media agent becomes unavailable,the system can identify the signatures that are assigned to be stored inthe third DDB media agent. Once the signatures assigned to the third DDBmedia agent are identified, the system can use modulo three to evenlydistribute those signatures to the three available DDB media agents.Thus, the system can maintain data integrity by continuing to use modulofour to evenly distribute the signatures amongst the four DDB mediaagents as if all four DDB media agents are available, and using modulothree to evenly distribute the signatures assigned to the third DDBmedia agent to the remaining available DDB media agents.

FIG. 3 is a data flow diagram illustrative of the interaction betweenthe various components of the system 100 when a DDB media agent isunavailable. While described with respect to backup for the purposes ofillustration, the techniques described herein are compatible with othertypes of storage operations, such as, for example, replication,snapshots, archiving, pruning, and the like.

The illustrated embodiment includes a client computing device 102 withan associated primary storage device 104, deduplication database mediaagents 304A, 304B, 304C (referred to generically as “DDB media agent304”), deduplication databases 306A, 306B, 306C, each associated withone of the DDB media agents (referred to generically as “DDB 306”),media agents 144A, 144B (referred to generically as “media agent 144”),and secondary storage devices 108, each of which is described in greaterdetail above. The other components of the system 100 are not shown forpurposes of simplicity.

Furthermore, while a single client 102 is shown for the purpose ofillustration, there may be more than one client in other embodiments.Similarly, there can be any number of DDB media agents (e.g., one ormore) and media agents (e.g., one or more). Additionally, in certainembodiments, some of the components shown as separate components in FIG.3 can reside on a single computing device. In some embodiments, forexample, the functionality of the DDB media agent 306A and the mediaagent 144A can be implemented on a first computing device, thefunctionality of the DDB media agent 306B and the media agent 144B canbe implemented on another computing device, etc.

In the illustrated embodiment, the data blocks (or other units) insecondary storage are stored separately from the deduplicationmanagement information. For example, in some embodiments, the mediaagents 144 aid in the storage of the data blocks in the secondarystorage devices 108. In contrast, the DDB media agents 304 store thededuplication management information such as data block signatures(e.g., hashes) and storage location information for the data blocks inthe secondary storage devices 108. The location information for the datablocks stored in the secondary storage devices 108 can also be referredto as a link.

Generally, deduplication management information can include anyappropriate information used to manage the deduplication process. As anexample, in addition to deduplication signatures, the managementinformation can further include metadata related to the deduplicateddata blocks. For instance, a count value may be maintained for eachdeduplicated data block that indicates the number of times theparticular data block is being used. As one example, if two files eachinclude three instances of a particular data block, and a third fileincludes one instance of the data block, the count for that data blockwould be seven. The management information can further include addressesor other location information related to the data blocks. As yet anotherexample, the management information can include mappings of theindividual deduplicated files including pointers to the data blocksmaking up the files and an indication as to the ordering of the datablocks within the files.

As described above, the signature can be generated using a hash functionor some other function, and can be used by the system 100 to determinewhether the data block already exists in the storage system. Thesignature can also be used to determine the location of data blockswithin the secondary storage devices 108 and the like. As described,location information is associated with each signature and is used bythe system 100 to locate and retrieve specific data blocks.

In one embodiment, the link includes a media agent ID indicating whichmedia agent 144 was used to store the data block, and a path ID, addressand offset indicating where the data block stored in the secondarystorage devices 108, The location information or link can generallyinclude various types of media agent identifiers, directory names,filenames, address locations, pointers, offsets, and the like, which canaid the system in locating individual data blocks. The media agentidentifiers can include MAC addresses, IP addresses, router information,directory information, filenames and/or other alphanumeric identifierscapable of uniquely identifying the different media agents 144. Thus,the DDB media agents 304 store signatures and links to data blocksstored within the secondary storage devices 108. The links can include,without limitation, a signature associated with the block andidentifiers indicative of the location of the data block. The locationalidentifiers can include positional information such as the relevanthost, mount point, file identifier, offset and size of the block, etc.

As will be described in greater detail below, the media agents 144 usethe links during storage operations to reference data blocks alreadystored in secondary storage (i.e. redundant data blocks). The mediaagents 144 can also use the links during restore operations to locateand retrieve data blocks stored in the secondary storage devices 108.

In the illustrated embodiment, the media agents 144 store files receivedfrom the client as a plurality of individual data blocks in secondarystorage. In some embodiments, the data blocks associated with a specificfile can be distributed across multiple media agents 144.

As mentioned previously, the system 100 can use various distributionpolicies to determine which media agents 144 store which data blocks. Insome embodiments, the system selects a media agent 144 to backup aparticular file (or block(s) in a file) based on a predetermineddistribution policy. For instance, the system 100 can perform a moduloor other appropriate operation on the signature of the file (or block(s)in the file) and select the appropriate media agent based on the outputof the operation.

Similarly, the storage system can use similar data block distributionpolicies to identify a media agent 144 storing a particular file forpurposes of a restore operation. In one embodiment, the storage manageror another component can track which media agent 144 handled the backupoperation, and send the restore request to that media agent 144.

With further reference to FIG. 3, the interaction between the variouscomponents of the storage environment when one of the DDB media agentsbecomes unavailable will now be described in greater detail with respectto data flow steps indicated by the numbered arrows. In the illustratedembodiment, there are three DDB media agents 304A, 304B, 304C and modulo3 is used to distribute the signatures between the three DDB mediaagents. It will be understood that functions other than a modulo may beused. For example, the storage system can distribute queries to therespective DDB media agents based on factors other than the modulo ofthe signature, e.g., based on file type, client source, modulo of thedata block, pseudo-randomly, etc.

Furthermore, in the illustrated embodiment, each DDB media agent 304acts as a failover DDB media agent for another DDB media agent. Forexample, in the illustrated embodiment, DDB media agent1 304A is thefailover DDB media agent for DDB media agent3 304C, DDB media agent2304B is the failover DDB media agent for DDB media agent1 304A, and DDBmedia agent3 304C is the failover DDB media agent for DDB media agent2304B. In addition, in the illustrated embodiment, the system 100 hasdetermined that DDB media agent1 304A is unavailable.

At step 1, the client 102 initiates a storage operation of a file storedin the primary storage device 104. In the illustrated embodiment, themedia agent2 144B is selected to handle the storage operation based onthe distribution policy. As mentioned previously, any one of the mediaagents 144 can be selected to handle the storage operation according tothe particular predetermined policy.

As part of the storage operation, the file is broken up into datablocks, and the media agent2 144B performs a signature function on eachdata block. In the illustrated embodiment, each data block is sent tothe media agent2 144B for storage, based on the predefined distributionpolicy. In some embodiments, a data agent residing on the clientperforms the signature function on the data block and the signature isinitially sent to the media agent2 144B. If it is determined that thedata block is not stored in secondary storage, the data block is sent aswell.

Before storing a copy of each data block in secondary storage, the mediaagent2 144B determines whether the identified data block is alreadystored in the secondary storage devices 108 by consulting one of the DDBmedia agents 304. As mentioned previously, the DDB media agents 304store signatures of the data blocks stored in the secondary storagedevices 108, and the signatures are distributed amongst the DDB mediaagents based on a distribution policy. Having knowledge of this policy,the media agents 144 can advantageously identify the appropriate DDBmedia agent 304 to query regarding the presence of the data block insecondary storage. In the present example, the distribution policydictates that a modulo of the signature of the data block is used toselect the appropriate DDB media agent 304.

Accordingly, at step 2, the media agent2 144B performs the modulooperation on the signature of the data block and identifies the DDBmedia agent assigned to store the signature. Based on the output of themodulo operation, the media agent2 144B, determines that the DDB mediaagent1 304A is assigned to store the signature corresponding to the datablock.

As mentioned, in the illustrated embodiment, the system 100 has detectedthat the DDB media agent1 304A is unavailable. Thus, as part of step 2,the media agent2 144B can identify the failover DDB media agent (DDBmedia agent2 304B) for DDB media agent1 304A and determine that thefailover DDB media agent is to be queried for the signature. The mediaagent2 can identify the failover DDB media agent by referring to thedistribution policy and/or a failover policy, as described in greaterdetail above. The media agent2 144B can determine that the failover DDBmedia agent is to be queried for the signature dynamically or based oninformation that is stored at the time the system detects that the DDBmedia agent1 304A is unavailable.

At step 3 the media agent2 144B queries the failover DDB media agent(DDB media agent2 304B) for the signature. At step 4, the DDB mediaagent2 304B responds. If the DDB media agent2 304B locates an entry inits DDB 306B corresponding to the signature, the DDB media agent2 304Baccesses the entry. According to certain embodiments, the entry caninclude a copy of the signature, a link identifying the location of thecorresponding data block in the secondary storage devices 108, and acount value. The count value can correspond to a number of instances ofthe particular data block in the files or other data stored in thesecondary storage devices 108. For instance, while there may only be onestored copy of the data block in the secondary storage devices 108,because of the deduplication, multiple files stored in the secondarystorage devices 108 may point to the copy of the data block. The DDBmedia agent 2 304B forwards the link to media agent 2 144B. Uponreceiving the link, the media agent2 144B can store the link or othermetadata representative of the data block in the secondary storagedevices 108 instead of storing another copy of the data block.

In the event that the DDB media agent2 304B does not find the signature,the DDB media agent2 304B responds to the media agent2 144B indicatingthat the data block is not stored in secondary storage. In turn, themedia agent 2 144B stores the data block in the secondary storagedevices 108. The media agent2 144B can also send the signature of thedata block as well as location information indicating where the datablock is stored in the secondary storage devices 108 to the DDB mediaagent2 304B. Upon receiving the signature and the location information,the DDB media agent2 304B uses the location information to generate alink for the data block and stores the link and/or signature in DDB 306Afor future reference.

Alternatively, once the DDB media agent2 304B determines that the datablock is not stored in secondary storage, it stores the signature in theDDB 306A before responding to the media agent2 144B. In response, themedia agent2 144B stores the data block, as discussed above, and sendsthe location information of the data block to the DDB media agent2 304B.In turn, the DDB media agent2 304B generates the link and stores thelink in the DDB 306A along with the already-stored signature. Inaddition to the examples provided, it will be appreciated that a varietyof other handshaking mechanisms are possible between the media agents144 and the DDB media agents 304.

The remaining data blocks of the file are backed up to the media agent2144B in a similar fashion, wherein copies of the data blocks themselvesare stored for new data blocks and links to redundant data blocks arestored in the secondary storage devices 108, as appropriate.

A similar process can be used to prune data from secondary storage. Forexample, when data is removed from the secondary storage devices 108 tolong-term storage (e.g. magnetic tape), steps 1-3 can be used to querythe appropriate DDB media agent to reduce the count value of aparticular data block signature. For instance, when a particular datablock is removed, the selected media agent (e.g., media agent 144B) usesthe distribution scheme to query the appropriate DDB media agent 304(e.g., failover DDB media agent 2 304B). If a stored count valueassociated with the data block indicates that no more instances of thedata block exist in the secondary storage devices 108 (e.g., the countvalue of the signature is zero), the queried DDB media agent 304 candelete the signature from its DDB 306, and the media agent can removethe data block from the secondary storage devices 108. If, afterdeletion, the count value is greater than or equal to one, then one ormore instances of the data block will remain in the secondary storagedevices 108 following deletion, and the count value will decrementedwithout deleting the instance of the signature from the database 306.

FIG. 4 is a flow diagram of a routine implemented by the storage systemfor processing a storage operation and storing data blocks to secondarystorage. One skilled in the relevant art will appreciate that theelements outlined for routine 400 may be implemented by one or manycomputing devices/components that are associated with the storage system100. For example, the routine 400 can be implemented by any one, or acombination, of the client computing device 102, the data agent 142, thestorage manager 140, the secondary storage computing device 106,deduplication database media agent (DDB media agent) 304 (i.e. any oneof the DDB media agent 304A-304B), the media agent 144 (i.e. any one ofthe media agents 144A-144C) and the like. Accordingly, routine 400 hasbeen described as being generally performed by the system 100.

At block 402, the system 100 receives a storage operation request for adata block. The request can be received from the client, a new client,one client on behalf of another, a storage manager, the media agent, theDDB media agent, or the like. Alternatively, the system 100 can receivea signature of a data block or a file, as described above.

At block 404, the system 100 identifies the DDB media agent assigned tostore the signature corresponding to the data block. As mentionedpreviously, the signature can be calculated by a variety of componentsof the system and can be used to uniquely identify the data block.Further, the system 100 can identify the assigned DDB media agent usingany number of techniques. In some embodiments, the system 100 performs amodulo operation on the signature of the data block to identify the DDBmedia agent assigned to store the signature associated with the datablock.

At block 406, the system 100 determines that the assigned DDB mediaagent is unavailable. The DDB media agent may become unavailable due todue to a network outage, power outage, hardware/software malfunction,scheduled maintenance, etc. The system can determine the DDB media agentis not available by requesting status updates from the different DDBmedia agents, reviewing status updates automatically sent by the DDBmedia agents, etc.

At block 408, the system 100 identifies a failover DDB media agent. Forexample, the system 100 may identify the failover DDB media agent byconsulting the distribution policy, which stores an indication of thefailover DDB media agent. The distribution policy can specify thefailover DDB media agents for each DDB media agent in the system 100. Inother embodiments, the failover DDB media agent is stored in a datastructure that is separate from the distribution policy. In someembodiments, the system 100 identifies the failover DDB media agent atthe time the system 100 detects that a DDB media agent is unavailable,and stores an indication of the unavailable DDB media agent and theappropriate failover DDB media agent in conjunction with thedistribution policy, or in a separate location, depending on theembodiment. In certain embodiments, the system 100 identifies thefailover DDB media agent dynamically, each time a data block is stored,e.g., when the unavailable DDB media agent is identified as the DDBmedia agent assigned to store the signature corresponding to the datablock.

The system 100 can use a variety of techniques to determine which DDBmedia agent is the failover DDB media agent for each DDB media agent. Insome embodiments, each DDB media agent is a failover for another DDBmedia agent. In certain embodiments, the DDB media agents are notfailover DDB media agents for each other (i.e. if DDB media agent1 isthe failover DDB media agent for DDB media agent2 then DDB media agent2is not the failover DDB media agent for DDB media agent1). In someembodiments, the DDB media agents are failover DDB media agents for atmost one other DDB media agent. In certain embodiments, one DDB mediaagent is the failover DDB media agent for multiple DDB media agents. Thedistribution policy can use any one or a combination of theaforementioned embodiments, or other techniques, to assign one or morefailover DDB media agents for each DDB media agent.

At block 410, the system 100 queries the failover DDB media agent forthe data block location. Following the query, the system 100 determineswhether the data block is located in secondary storage using informationfound in the DDB media agent.

One skilled in the art will appreciate that routine 400 can includefewer, more, or different blocks than those illustrated in FIG. 4without departing from the spirit and scope of the description. In someembodiments, any one, or a combination of the blocks 412, 414, 416 canbe used as part of the routine 400. For example, if the storageoperation is a backup operation and the signature is not stored in thefailover DDB media agent, the system 100 can store the signature in thefailover DDB media agent, as illustrated at block 412. In addition, acopy of the data block can be stored in the secondary storage devices108 and the location of the copy can be sent to the failover DDB mediaagent for storage.

In some embodiments, if the signature is stored in the failover DDBmedia agent, the system 100 can store a link to the copy of the datablock stored in the secondary storage devices 108 and increment a countvalue in the DDB media agent to indicate that a new instance of the datablock has been backed up, as illustrated at block 414.

In certain embodiments, if the storage operation is a pruning operation,the system can decrement the count value in the DDB media agent, asillustrated at block 416. Further, if the count value reaches zero, thesystem can remove the signature from the DDB media agent and delete thecopy of the data block from the secondary storage devices 108.

In addition, prior to querying the DDB media agent, the system can querythe database 152 of a media agent for the data block or the location ofthe data block. If the data block (or its locations) is not found in thedatabase 152 of the media agent, the system can query the DDB mediaagent or failover DDB media agent. If the data block is found in thedatabase 152 of the media agent, and the storage operation is a backupoperation, the system can store a link to the data block in the mediaagent and notify the DDB media agent, or failover DDB media agent, thata new instance of the data block is now found in the secondary storagedevices 108. In addition, the backup storage device can aggregate anumber of queries to the DDB media agent, and transmit all the queriestogether as a bundle.

In some embodiments, when an unavailable DDB media agent becomesavailable, the failover DDB media agent can copy the signatures thatwould have been stored on the unavailable DDB media agent if it had beenavailable to the previously unavailable DDB media agent. For example,entries in the DDB of the failover DDB media agent and correspondingfailover data blocks can be identified (e.g., using a modulo operation)and copied to the DDB of the previously unavailable DDB media agentwhich has come back on-line. As part of the copy operation, thepreviously unavailable DDB media agent and the failover DDB media agentcan synchronize the data to remove duplicate signatures and data blocks.As part of the synchronization process, the system can remove duplicatedata blocks in the secondary storage and update the links in thesecondary storage devices that reference the duplicate data blocks.Following the synchronization process, the system can avoid referring tothe failover DDB media agent during future copy operations while thepreviously unavailable DDB media agent is available.

In addition to the embodiments described above with reference to FIGS.1A-1E and 2A, the system can include a failover index 308. In theillustrated embodiment of FIG. 3, a failover index is included in eachof the media agents 144A-144C (failover indexes 308A-308C, respectively)and can be implemented as part of the database 152 and/or index 153,described previously, or can be a separate index. However, it will beunderstood that the failover index can be located in the client 102,data agent 142, storage manager 140, in the DDB media agents 304, etc.

The failover index 308 can store the failover policy for the system.Thus, the failover index 308 can be used by the system to determine thefailover DDB media agent(s) for each DDB media agent. Furthermore, insome embodiments, the failover index 308 can store additionalinformation that can be used when a DDB media agent becomes unavailable,and after the DDB media agent comes back on-line. For example, as willbe described in greater detail below, the failover index 308 can trackwhich DDB media agents are unavailable, the amount of time a DDB mediaagent is unavailable, signatures that were stored in a failover DDBmedia agent as a result of the unavailability of another DDB mediaagent, location information for data blocks in secondary storage thatwere stored when the assigned DDB media agent was unavailable, etc.

In some embodiments, the failover index can track which DDB media agentshave been unavailable and their corresponding failover DDB media agents.Once an unavailable DDB media agent becomes available and the systemqueries it for a signature, if the signature is not found, the systemcan query the failover DDB media agent for the signature. For example,assuming DDB media agent1 304A has been unavailable, the system canrecord that DDB media agent1 304A was unavailable and also record theidentity of the failover DDB media agent (DDB media agent2 304B) thatstored any signatures on behalf of the DDB media agent1 304A. After theDDB media agent1 304A comes back on-line and following a failed query tothe DDB media agent1 304A (e.g. the signature was not found), the systemcan use the tracked information to query the failover DDB media agentfor the signature.

Furthermore, in certain embodiments, the failover index 308 can storesignature information when a DDB media agent becomes unavailable and afailover DDB media agent is used. For example, if DDB media agent1 304Abecomes unavailable and signatures assigned to be stored in DDB mediaagent1 304A are stored in DDB media agent2 304B (the failover DDB mediaagent), the failover index 308B can track the signatures that are storedin the failover DDB media agent (DDB media agent2 304B), for laterreference by the system. The failover index 308 can include thesignatures stored in failover DDB media agents when a DDB media agent isunavailable, as well as location information of the signatures,including where the signature is located in the failover DDB mediaagent.

In some embodiments, the failover index 308 can be used as the failoverDDB media agent. For example, when a DDB media agent becomesunavailable, the signatures that would have been stored in theunavailable DDB media agent can be stored in the failover index 308.Thus, when a media agent 144 receives a signature for the unavailableDDB media agent, it can refer to the failover index 308. If thesignature is not found in the failover index 308, a copy of the datablock can be stored in the secondary storage devices, and the locationof the copied data block and a copy of the signature can be stored inthe failover index 308. If the signature is found in the failover index308, the media agent 144 can use the location information of the copieddata block that is stored in the failover index 308 as part of thebackup operation. When the unavailable DDB media agent becomesavailable, the failover index can copy and synchronize its contents withthe previously unavailable DDB media agent.

FIG. 5 is a data flow diagram illustrative of the interaction betweenthe various components of the system 100 after a previously unavailableDDB media agent becomes available. While described with respect tobackup for the purposes of illustration, the techniques described hereinare compatible with other types of storage operations, such as, forexample, replication, snapshots, archiving, pruning, and the like.

At step 5, the client 102 initiates a storage operation of a file storedin the primary storage device 104. As mentioned previously, a signaturefor each data block in the file is determined. In addition, prior tostoring a copy of each data block, the media agent2 144B determineswhether the received data block is already stored in the secondarystorage devices 108 by consulting one of the DDB media agents 304.

At step 6, the media agent2 144B performs a DDB media agent identifieroperation on the signature of the data block to identify the DDB mediaagent 304 assigned to store the signature. Based on the output of theoperation, the media agent2 144B, determines that the DDB media agent1304A is assigned to store the signature corresponding to the data block.

However, as discussed in greater detail above with reference to FIG. 3,as DDB media agent1 304A was previously unavailable, some signaturesthat would have been stored in DDB media agent1 304A were stored in thefailover DDB media agent (DDB media agent2 304C). Accordingly, as partof step 6, the media agent2 144B determines whether the signature wasstored in the failover DDB media agent. The system can determine thatthe signature was stored in the failover DDB media agent using a varietyof techniques. For example, the system can use the DDB media agentfailover index 308B to track the signatures stored in a failover DDBmedia agent while the DDB media agent1 304A was unavailable. Asdiscussed previously, the failover index 308B can include the signatureof the data block as well as an identifier indicating in which failoverDDB media agent the signature is located. If the signature is found inthe failover index 308B, the system can determine that the signature wasstored in the failover DDB media agent.

At step 7 in the illustrated embodiment, the media agent2 144Bdetermines that the signature was stored in the DDB media agent2 304B(the failover DDB media agent for DDB media agent1 304A) and queries thefailover DDB media agent for the signature and the location of the datablock. The failover DDB media agent can increment the count value of thesignature.

Similarly, if the storage operation is a pruning operation and thesystem determines that the signature is stored in the failover DDB mediaagent, the system can decrement the count value in the failover DDBmedia agent. If the count value in the failover DDB media agentindicates there are no more instances of the data block in the secondarystorage devices 108, the system can delete the copy of the data blockthat is referenced by the signature in the failover DDB media agent.However, it will be understood that there may still be a copy of thedata block in the secondary storage devices 108 that is identified bythe assigned DDB media agent.

In some embodiments, if the system determines that the signature was notstored in the failover DDB media agent, the system can use the assignedDDB media agent to store the signature, retrieve the location of thedata block, and/or increment/decrement the count value of the signature,according to the distribution policy. Thus, the system can use thefailover DDB media agent for the signatures stored thereon while theother DDB media agent was unavailable and use the assigned DDB mediaagent for all other signatures.

At step 8, the failover DDB media agent provides the signatureinformation to the media agent2 144B. As mentioned previously, thesignature information can include location information regarding thelocation of the data block in the secondary storage devices 108.

FIG. 6 is a flow diagram of a routine implemented by the storage systemfor processing a storage operation and storing data blocks to secondarystorage. One skilled in the relevant art will appreciate that theelements outlined for routine 600 may be implemented by one or manycomputing devices/components that are associated with the storage system100. For example, the routine 600 can be implemented by any one, or acombination, of the client computing device 102, the data agent 142, thestorage manager 140, the secondary storage computing device 106,deduplication database media agent (DDB media agent) 304 (i.e. any oneof the DDB media agent 304A-304B), the media agent 144 (i.e. any one ofthe media agents 144A-144C) and the like. Accordingly, routine 600 hasbeen logically associated as being generally performed by the system100, and thus the following illustrative embodiments should not beconstrued as limiting.

At block 602, the system 100 receives a storage operation request for adata block. The request can be received from the client, a new client,one client on behalf of another, a storage manager, the media agent, theDDB media agent, or the like. Alternatively, the system 100 can receivea signature of a data block or a file, as described above.

At block 604, the system 100 identifies the DDB media agent assigned tostore the signature corresponding to the data block. As mentionedpreviously, the signature can be calculated by a variety of componentsof the system and can be used to uniquely identify the data block.Further, the system 100 can identify the assigned DDB media agent usingany number of techniques. In some embodiments, the system 100 performs amodulo operation on the signature of the data block to identify the DDBmedia agent assigned to store the signature associated with the datablock.

At block 606, the system 100 determines that although the signature isassigned to be stored in the assigned DDB media agent, the signature isstored in a failover DDB media agent. As discussed in greater detailabove, this can be due to the unavailability of the assigned DDB mediaagent for a period of time and the system 100 assigning the failover DDBmedia agent to handle signature queries for the assigned DDB mediaagent.

At block 608, the system 100 queries the failover DDB media agent forthe data block location. Based on the query the failover DDB media agentcan increment or decrement the count value of the associated signature,as discussed in greater detail above with reference to FIG. 4. If thecount value is decremented to zero, the system 100 can remove thecorresponding data block from the secondary storage devices 108 and canremove the signature from the failover DDB media agent.

One skilled in the art will appreciate that routine 600 can includefewer, more, or different blocks than those illustrated in FIG. 6without departing from the spirit and scope of the description. Forexample, in some embodiments, the system can query the failover DDBmedia agent only if the signature is not found in the assigned DDB mediaagent.

FIG. 7 is a block diagram illustrative of an embodiment of multiple DDBmedia agents (DDB media agent 702, DDB media agent 704, DDB media agent706, DDB media agent 708) arranged as logical partitions of a globaldeduplication database 701. As illustrated in FIG. 7, each of the DDBmedia agents 702-708 can be associated with a partition (partitions712-718, respectively) of the database 701. Specifically, the database710 of each DDB media agent 702-708 (databases 710A-710D, respectively)can correspond to the partitions 712-718 of the global deduplicationdatabase 701. The global deduplication database 701 can be a distributeddatabase arranged on separate computing devices or be part of a singlecomputing device. For example, each DDB media agent 702-708 cancorrespond to a separate computing device with separate storage or oneor more DDB media agents 702-708 can reside on a single computingdevice. In this way, the DDB media agents 702-708 can be treated as asingle database for access purposes. When a DDB media agent becomesunavailable, the partition of the database 701 previously assigned tothe unavailable DDB media agent is assigned to the DDB media agentdesignated (e.g., by a round-robin or other failover policy) as thefailover DDB media agent. For instance, if DDB media agent 702 becomesunavailable and DDB media agent 704 is the failover DDB media agent 702according to the failover policy, the partition 712 of the database 701may be assigned to DDB media agent 704 as a result of the unavailabilityof DDB media agent 702. At that point, DDB media agent 704 is associatedwith both the partition 712 that was previously assigned to the nowunavailable DDB media agent 702 as well as the partition 714 originallyassigned to DDB media agent 704. If DDB media agent 702 becomesavailable again, the storage manager or other appropriate entity mayre-associate partition 712 back to DDB media agent 702.

Terminology

Conditional language, such as, among others, “can,” “could,” “might,” or“may,” unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements and/or steps areincluded or are to be performed in any particular embodiment.

Depending on the embodiment, certain acts, events, or functions of anyof the algorithms described herein can be performed in a differentsequence, can be added, merged, or left out all together (e.g., not alldescribed acts or events are necessary for the practice of thealgorithms). Moreover, in certain embodiments, acts or events can beperformed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors or processor cores or onother parallel architectures, rather than sequentially.

Systems and modules described herein may comprise software, firmware,hardware, or any combination(s) of software, firmware, or hardwaresuitable for the purposes described herein. Software and other modulesmay reside on servers, workstations, personal computers, computerizedtablets, PDAs, and other devices suitable for the purposes describedherein. Software and other modules may be accessible via local memory,via a network, via a browser, or via other means suitable for thepurposes described herein. Data structures described herein may comprisecomputer files, variables, programming arrays, programming structures,or any electronic information storage schemes or methods, or anycombinations thereof, suitable for the purposes described herein. Userinterface elements described herein may comprise elements from graphicaluser interfaces, command line interfaces, and other suitable interfaces.

Further, the processing of the various components of the illustratedsystems can be distributed across multiple machines, networks, and othercomputing resources. In addition, two or more components of a system canbe combined into fewer components. Various components of the illustratedsystems can be implemented in one or more virtual machines, rather thanin dedicated computer hardware systems. Likewise, the data repositoriesshown can represent physical and/or logical data storage, including, forexample, storage area networks or other distributed storage systems.Moreover, in some embodiments the connections between the componentsshown represent possible paths of data flow, rather than actualconnections between hardware. While some examples of possibleconnections are shown, any of the subset of the components shown cancommunicate with any other subset of components in variousimplementations.

Embodiments are also described above with reference to flow chartillustrations and/or block diagrams of methods, apparatus (systems) andcomputer program products. Each block of the flow chart illustrationsand/or block diagrams, and combinations of blocks in the flow chartillustrations and/or block diagrams, may be implemented by computerprogram instructions. Such instructions may be provided to a processorof a general purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the acts specified in the flow chart and/or block diagramblock or blocks.

These computer program instructions may also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to operate in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instruction meanswhich implement the acts specified in the flow chart and/or blockdiagram block or blocks. The computer program instructions may also beloaded onto a computer or other programmable data processing apparatusto cause a series of operations to be performed on the computer or otherprogrammable apparatus to produce a computer implemented process suchthat the instructions which execute on the computer or otherprogrammable apparatus provide steps for implementing the acts specifiedin the flow chart and/or block diagram block or blocks.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the describedmethods and systems may be made without departing from the spirit of thedisclosure. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the disclosure.

What is claimed is:
 1. A method of performing a storage operation in adistributed, deduplicated storage system, comprising: receiving at afirst secondary storage computing device of a plurality of secondarystorage computing devices a request from a client computing device tobackup a file comprising a plurality of data blocks and stored inprimary storage, wherein a first deduplication database computing deviceof a plurality of deduplication database computing devicescommunicatively coupled to the first secondary storage computing deviceis configured to store a first subset of signature blocks based at leastin part on a data block distribution policy and is designated as afailover deduplication database computing device for a seconddeduplication database computing device of the plurality ofdeduplication database computing devices that is configured to store,based at least in part on the data block distribution policy, a secondsubset of the signature blocks that is different from and does notoverlap with the first subset of the signature blocks, wherein theplurality of deduplication database computing devices store thesignature blocks corresponding to data blocks stored in secondarystorage, wherein the data blocks stored in the secondary storagecorrespond to data blocks stored in primary storage, at least onesignature block of the signature blocks comprising a signature of atleast one data block of the plurality of data blocks, locationinformation of the at least one data block in the secondary storage, anda reference count value indicative of a quantity of one or morereferences in the secondary storage to the at least one data block; inresponse to the request and using one or more processors, calculating asignature of a particular data block of the plurality of data blocksusing a signature function; identifying the second deduplicationdatabase computing device as the deduplication database computing deviceassigned to store the signature of the particular data block;determining that the second deduplication database computing device isunavailable; and querying the first deduplication database computingdevice for the signature of the particular data block, the methodfurther comprising at least one of: based at least in part on anindication from the first deduplication database computing device thatthe signature of the particular data block does not reside in the firstdeduplication database computing device, store the signature in afailover index, cause at least one storage device of the of thesecondary storage to store a copy of the particular data block, andrequest the first deduplication database computing device to store thesignature of the particular data block and a location of the copy of theparticular data block, or based at least in part on an indication fromthe first deduplication database computing device that the signature ofthe particular data block resides in the first deduplication databasecomputing device, cause at least one storage device of the of thesecondary storage to store a reference to a copy of the particular datablock that is stored in the secondary storage.
 2. The method of claim 1,wherein each deduplication database computing device is assigned tostore a different group of unique signatures.
 3. The method of claim 1,wherein the first deduplication database computing device is assigned tostore a first set of signatures and the second deduplication databasecomputing device is assigned to store a second set of signaturesdifferent from the first set of signatures.
 4. The method of claim 1,wherein each deduplication database computing device of the plurality ofdeduplication database computing devices is identified as a failoverdeduplication database computing device to another one of the pluralityof deduplication database computing devices.
 5. The method of claim 1,further comprising identifying a third deduplication database computingdevice as the failover deduplication database computing device for thefirst deduplication database computing device and identifying the seconddeduplication database computing device as the failover deduplicationdatabase computing device for the third deduplication database computingdevice.
 6. The method of claim 1, further comprising calculating asignature of each of the plurality of data blocks using the signaturefunction.
 7. A distributed deduplicated storage system, comprising: aplurality of deduplication database computing devices configured tostore signature blocks corresponding to a plurality of data blocksstored in one or more storage devices of secondary storage, at least onesignature block of the signature blocks comprising a signature of atleast one data block of the plurality of data blocks, locationinformation of the at least one data block in the one or more storagedevices, and a reference count value indicative of a quantity of one ormore references in the secondary storage to the at least one data block,wherein a first deduplication database computing device of the pluralityof deduplication database computing devices is configured to store afirst subset of the signature blocks based at least in part on a datablock distribution policy and is designated as a failover deduplicationdatabase computing device for a second deduplication database computingdevice of the plurality of deduplication database computing devices thatis configured to store, based at least in part on the data blockdistribution policy, a second subset of the signature blocks that isdifferent from and does not overlap with the first subset of thesignature blocks; and a plurality of secondary storage computing devicescommunicatively coupled to the plurality of deduplication databasecomputing devices, each of the plurality of secondary storage computingdevices comprising one or more processors and storage, wherein at leastone secondary storage computing device of the plurality of secondarystorage computing devices further comprises a failover index and isconfigured to: receive a request to backup a file comprising a pluralityof data blocks and stored in primary storage, calculate a signature of aparticular data block of the plurality of data blocks using a signaturefunction, identify the second deduplication database computing device asthe deduplication database computing device assigned to store thesignature of the particular data block, determine that the seconddeduplication database computing device is unavailable, and query thefirst deduplication database computing device for the signature of theparticular data block, wherein the at least one secondary storagecomputing device is further configured to at least one of: based atleast in part on an indication from the first deduplication databasecomputing device that the signature of the particular data block doesnot reside in the first deduplication database computing device, storethe signature in the failover index, cause at least one storage deviceof the one or more storage devices of the secondary storage to store acopy of the particular data block, and request the first deduplicationdatabase computing device to store the signature of the particular datablock and a location of the copy of the particular data block, or basedat least in part on an indication from the first deduplication databasecomputing device that the signature of the particular data block residesin the first deduplication database computing device, cause at least onestorage device of the one or more storage devices of the secondarystorage to store a reference to a copy of the particular data block thatis stored in the secondary storage.
 8. The system of claim 7, whereineach deduplication database computing device is assigned to store uniquesignatures of different data blocks.
 9. The system of claim 7, whereinthe first deduplication database computing device is assigned to store afirst set of signatures and the second deduplication database computingdevice is assigned to store a second set of signatures different fromthe first set of signatures.
 10. The system of claim 7, wherein eachdeduplication database computing device of the plurality ofdeduplication database computing devices is identified as a failoverdeduplication database computing device to another one of the pluralityof deduplication database computing devices.
 11. The system of claim 7,further comprising a third deduplication database computing deviceidentified as the failover deduplication database computing device forthe first deduplication database computing device, wherein the seconddeduplication database computing device is identified as the failoverdeduplication database computing device for the third deduplicationdatabase computing device.
 12. The system of claim 7, wherein the atleast one of the plurality of secondary storage computing devices isfurther configured to calculate a signature of each of the plurality ofdata blocks using the signature function.